third_party/WebKit/Source/core/dom/Element.cpp

/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 1999 Antti Koivisto (koivisto@kde.org)
 *           (C) 2001 Peter Kelly (pmk@post.com)
 *           (C) 2001 Dirk Mueller (mueller@kde.org)
 *           (C) 2007 David Smith (catfish.man@gmail.com)
 * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc.
 * All rights reserved.
 *           (C) 2007 Eric Seidel (eric@webkit.org)
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#include "core/dom/Element.h"

#include "bindings/core/v8/DOMDataStore.h"
#include "bindings/core/v8/Dictionary.h"
#include "bindings/core/v8/ExceptionMessages.h"
#include "bindings/core/v8/ExceptionState.h"
#include "bindings/core/v8/V8DOMActivityLogger.h"
#include "bindings/core/v8/V8DOMWrapper.h"
#include "bindings/core/v8/V8PerContextData.h"
#include "core/CSSValueKeywords.h"
#include "core/SVGNames.h"
#include "core/XMLNames.h"
#include "core/animation/AnimationTimeline.h"
#include "core/animation/CustomCompositorAnimations.h"
#include "core/animation/css/CSSAnimations.h"
#include "core/css/CSSIdentifierValue.h"
#include "core/css/CSSImageValue.h"
#include "core/css/CSSPrimitiveValue.h"
#include "core/css/CSSStyleSheet.h"
#include "core/css/PropertySetCSSStyleDeclaration.h"
#include "core/css/StylePropertySet.h"
#include "core/css/parser/CSSParser.h"
#include "core/css/resolver/SelectorFilterParentScope.h"
#include "core/css/resolver/StyleResolver.h"
#include "core/css/resolver/StyleResolverStats.h"
#include "core/css/resolver/StyleSharingDepthScope.h"
#include "core/dom/AXObjectCache.h"
#include "core/dom/Attr.h"
#include "core/dom/CSSSelectorWatch.h"
#include "core/dom/ClientRect.h"
#include "core/dom/ClientRectList.h"
#include "core/dom/DatasetDOMStringMap.h"
#include "core/dom/ElementDataCache.h"
#include "core/dom/ElementRareData.h"
#include "core/dom/ElementTraversal.h"
#include "core/dom/ExceptionCode.h"
#include "core/dom/FirstLetterPseudoElement.h"
#include "core/dom/Fullscreen.h"
#include "core/dom/LayoutTreeBuilder.h"
#include "core/dom/MutationObserverInterestGroup.h"
#include "core/dom/MutationRecord.h"
#include "core/dom/NamedNodeMap.h"
#include "core/dom/NodeComputedStyle.h"
#include "core/dom/NodeIntersectionObserverData.h"
#include "core/dom/PresentationAttributeStyle.h"
#include "core/dom/PseudoElement.h"
#include "core/dom/ScriptableDocumentParser.h"
#include "core/dom/SelectorQuery.h"
#include "core/dom/StyleChangeReason.h"
#include "core/dom/StyleEngine.h"
#include "core/dom/Text.h"
#include "core/dom/custom/CustomElement.h"
#include "core/dom/custom/CustomElementRegistry.h"
#include "core/dom/custom/V0CustomElement.h"
#include "core/dom/custom/V0CustomElementRegistrationContext.h"
#include "core/dom/shadow/ElementShadow.h"
#include "core/dom/shadow/ElementShadowV0.h"
#include "core/dom/shadow/InsertionPoint.h"
#include "core/dom/shadow/ShadowRoot.h"
#include "core/dom/shadow/ShadowRootInit.h"
#include "core/dom/shadow/SlotAssignment.h"
#include "core/editing/EditingUtilities.h"
#include "core/editing/FrameSelection.h"
#include "core/editing/iterators/TextIterator.h"
#include "core/editing/serializers/Serialization.h"
#include "core/events/EventDispatcher.h"
#include "core/events/FocusEvent.h"
#include "core/frame/FrameHost.h"
#include "core/frame/FrameView.h"
#include "core/frame/HostsUsingFeatures.h"
#include "core/frame/LocalDOMWindow.h"
#include "core/frame/LocalFrame.h"
#include "core/frame/ScrollToOptions.h"
#include "core/frame/Settings.h"
#include "core/frame/UseCounter.h"
#include "core/frame/VisualViewport.h"
#include "core/frame/csp/ContentSecurityPolicy.h"
#include "core/html/ClassList.h"
#include "core/html/HTMLCanvasElement.h"
#include "core/html/HTMLCollection.h"
#include "core/html/HTMLDocument.h"
#include "core/html/HTMLElement.h"
#include "core/html/HTMLFormControlsCollection.h"
#include "core/html/HTMLFrameElementBase.h"
#include "core/html/HTMLFrameOwnerElement.h"
#include "core/html/HTMLOptionsCollection.h"
#include "core/html/HTMLPlugInElement.h"
#include "core/html/HTMLSlotElement.h"
#include "core/html/HTMLTableRowsCollection.h"
#include "core/html/HTMLTemplateElement.h"
#include "core/html/parser/HTMLParserIdioms.h"
#include "core/input/EventHandler.h"
#include "core/inspector/InspectorInstrumentation.h"
#include "core/layout/LayoutTextFragment.h"
#include "core/layout/api/LayoutBoxItem.h"
#include "core/layout/api/LayoutViewItem.h"
#include "core/loader/DocumentLoader.h"
#include "core/observer/ResizeObservation.h"
#include "core/page/ChromeClient.h"
#include "core/page/FocusController.h"
#include "core/page/Page.h"
#include "core/page/PointerLockController.h"
#include "core/page/SpatialNavigation.h"
#include "core/page/scrolling/RootScrollerController.h"
#include "core/page/scrolling/ScrollCustomizationCallbacks.h"
#include "core/page/scrolling/ScrollState.h"
#include "core/page/scrolling/ScrollStateCallback.h"
#include "core/page/scrolling/TopDocumentRootScrollerController.h"
#include "core/paint/PaintLayer.h"
#include "core/svg/SVGAElement.h"
#include "core/svg/SVGDocumentExtensions.h"
#include "core/svg/SVGElement.h"
#include "platform/EventDispatchForbiddenScope.h"
#include "platform/RuntimeEnabledFeatures.h"
#include "platform/UserGestureIndicator.h"
#include "platform/graphics/CompositorMutableProperties.h"
#include "platform/graphics/CompositorMutation.h"
#include "platform/scroll/ScrollableArea.h"
#include "wtf/BitVector.h"
#include "wtf/HashFunctions.h"
#include "wtf/text/CString.h"
#include "wtf/text/StringBuilder.h"
#include "wtf/text/TextPosition.h"
#include <memory>

namespace blink {

namespace {

// We need to retain the scroll customization callbacks until the element
// they're associated with is destroyed. It would be simplest if the callbacks
// could be stored in ElementRareData, but we can't afford the space
// increase. Instead, keep the scroll customization callbacks here. The other
// option would be to store these callbacks on the FrameHost or document, but
// that necessitates a bunch more logic for transferring the callbacks between
// FrameHosts when elements are moved around.
ScrollCustomizationCallbacks& scrollCustomizationCallbacks() {
  DEFINE_STATIC_LOCAL(ScrollCustomizationCallbacks,
                      scrollCustomizationCallbacks,
                      (new ScrollCustomizationCallbacks));
  return scrollCustomizationCallbacks;
}

}  // namespace

using namespace HTMLNames;
using namespace XMLNames;

enum class ClassStringContent { Empty, WhiteSpaceOnly, HasClasses };

Element* Element::create(const QualifiedName& tagName, Document* document) {
  return new Element(tagName, document, CreateElement);
}

Element::Element(const QualifiedName& tagName,
                 Document* document,
                 ConstructionType type)
    : ContainerNode(document, type), m_tagName(tagName) {}

Element::~Element() {
  DCHECK(needsAttach());
}

inline ElementRareData* Element::elementRareData() const {
  DCHECK(hasRareData());
  return static_cast<ElementRareData*>(rareData());
}

inline ElementRareData& Element::ensureElementRareData() {
  return static_cast<ElementRareData&>(ensureRareData());
}

bool Element::hasElementFlagInternal(ElementFlags mask) const {
  return elementRareData()->hasElementFlag(mask);
}

void Element::setElementFlag(ElementFlags mask, bool value) {
  if (!hasRareData() && !value)
    return;
  ensureElementRareData().setElementFlag(mask, value);
}

void Element::clearElementFlag(ElementFlags mask) {
  if (!hasRareData())
    return;
  elementRareData()->clearElementFlag(mask);
}

void Element::clearTabIndexExplicitlyIfNeeded() {
  if (hasRareData())
    elementRareData()->clearTabIndexExplicitly();
}

void Element::setTabIndexExplicitly(short tabIndex) {
  ensureElementRareData().setTabIndexExplicitly(tabIndex);
}

void Element::setTabIndex(int value) {
  setIntegralAttribute(tabindexAttr, value);
}

short Element::tabIndex() const {
  return hasRareData() ? elementRareData()->tabIndex() : 0;
}

bool Element::layoutObjectIsFocusable() const {
  // Elements in canvas fallback content are not rendered, but they are allowed
  // to be focusable as long as their canvas is displayed and visible.
  if (isInCanvasSubtree()) {
    const HTMLCanvasElement* canvas =
        Traversal<HTMLCanvasElement>::firstAncestorOrSelf(*this);
    DCHECK(canvas);
    return canvas->layoutObject() &&
           canvas->layoutObject()->style()->visibility() ==
               EVisibility::Visible;
  }

  // FIXME: Even if we are not visible, we might have a child that is visible.
  // Hyatt wants to fix that some day with a "has visible content" flag or the
  // like.
  return layoutObject() &&
         layoutObject()->style()->visibility() == EVisibility::Visible;
}

Node* Element::cloneNode(bool deep) {
  return deep ? cloneElementWithChildren() : cloneElementWithoutChildren();
}

Element* Element::cloneElementWithChildren() {
  Element* clone = cloneElementWithoutChildren();
  cloneChildNodes(clone);
  return clone;
}

Element* Element::cloneElementWithoutChildren() {
  Element* clone = cloneElementWithoutAttributesAndChildren();
  // This will catch HTML elements in the wrong namespace that are not correctly
  // copied.  This is a sanity check as HTML overloads some of the DOM methods.
  DCHECK_EQ(isHTMLElement(), clone->isHTMLElement());

  clone->cloneDataFromElement(*this);
  return clone;
}

Element* Element::cloneElementWithoutAttributesAndChildren() {
  return document().createElement(tagQName(), CreatedByCloneNode);
}

Attr* Element::detachAttribute(size_t index) {
  DCHECK(elementData());
  const Attribute& attribute = elementData()->attributes().at(index);
  Attr* attrNode = attrIfExists(attribute.name());
  if (attrNode) {
    detachAttrNodeAtIndex(attrNode, index);
  } else {
    attrNode = Attr::create(document(), attribute.name(), attribute.value());
    removeAttributeInternal(index, NotInSynchronizationOfLazyAttribute);
  }
  return attrNode;
}

void Element::detachAttrNodeAtIndex(Attr* attr, size_t index) {
  DCHECK(attr);
  DCHECK(elementData());

  const Attribute& attribute = elementData()->attributes().at(index);
  DCHECK(attribute.name() == attr->getQualifiedName());
  detachAttrNodeFromElementWithValue(attr, attribute.value());
  removeAttributeInternal(index, NotInSynchronizationOfLazyAttribute);
}

void Element::removeAttribute(const QualifiedName& name) {
  if (!elementData())
    return;

  size_t index = elementData()->attributes().findIndex(name);
  if (index == kNotFound)
    return;

  removeAttributeInternal(index, NotInSynchronizationOfLazyAttribute);
}

void Element::setBooleanAttribute(const QualifiedName& name, bool value) {
  if (value)
    setAttribute(name, emptyAtom);
  else
    removeAttribute(name);
}

NamedNodeMap* Element::attributesForBindings() const {
  ElementRareData& rareData =
      const_cast<Element*>(this)->ensureElementRareData();
  if (NamedNodeMap* attributeMap = rareData.attributeMap())
    return attributeMap;

  rareData.setAttributeMap(NamedNodeMap::create(const_cast<Element*>(this)));
  return rareData.attributeMap();
}

ElementAnimations* Element::elementAnimations() const {
  if (hasRareData())
    return elementRareData()->elementAnimations();
  return nullptr;
}

ElementAnimations& Element::ensureElementAnimations() {
  ElementRareData& rareData = ensureElementRareData();
  if (!rareData.elementAnimations())
    rareData.setElementAnimations(new ElementAnimations());
  return *rareData.elementAnimations();
}

bool Element::hasAnimations() const {
  if (!hasRareData())
    return false;

  ElementAnimations* elementAnimations = elementRareData()->elementAnimations();
  return elementAnimations && !elementAnimations->isEmpty();
}

Node::NodeType Element::getNodeType() const {
  return kElementNode;
}

bool Element::hasAttribute(const QualifiedName& name) const {
  return hasAttributeNS(name.namespaceURI(), name.localName());
}

void Element::synchronizeAllAttributes() const {
  if (!elementData())
    return;
  // NOTE: anyAttributeMatches in SelectorChecker.cpp
  // currently assumes that all lazy attributes have a null namespace.
  // If that ever changes we'll need to fix that code.
  if (elementData()->m_styleAttributeIsDirty) {
    DCHECK(isStyledElement());
    synchronizeStyleAttributeInternal();
  }
  if (elementData()->m_animatedSVGAttributesAreDirty) {
    DCHECK(isSVGElement());
    toSVGElement(this)->synchronizeAnimatedSVGAttribute(anyQName());
  }
}

inline void Element::synchronizeAttribute(const QualifiedName& name) const {
  if (!elementData())
    return;
  if (UNLIKELY(name == styleAttr && elementData()->m_styleAttributeIsDirty)) {
    DCHECK(isStyledElement());
    synchronizeStyleAttributeInternal();
    return;
  }
  if (UNLIKELY(elementData()->m_animatedSVGAttributesAreDirty)) {
    DCHECK(isSVGElement());
    // See comment in the AtomicString version of synchronizeAttribute()
    // also.
    toSVGElement(this)->synchronizeAnimatedSVGAttribute(name);
  }
}

void Element::synchronizeAttribute(const AtomicString& localName) const {
  // This version of synchronizeAttribute() is streamlined for the case where
  // you don't have a full QualifiedName, e.g when called from DOM API.
  if (!elementData())
    return;
  if (elementData()->m_styleAttributeIsDirty &&
      equalPossiblyIgnoringCase(localName, styleAttr.localName(),
                                shouldIgnoreAttributeCase())) {
    DCHECK(isStyledElement());
    synchronizeStyleAttributeInternal();
    return;
  }
  if (elementData()->m_animatedSVGAttributesAreDirty) {
    // We're not passing a namespace argument on purpose. SVGNames::*Attr are
    // defined w/o namespaces as well.

    // FIXME: this code is called regardless of whether name is an
    // animated SVG Attribute. It would seem we should only call this method
    // if SVGElement::isAnimatableAttribute is true, but the list of
    // animatable attributes in isAnimatableAttribute does not suffice to
    // pass all layout tests. Also, m_animatedSVGAttributesAreDirty stays
    // dirty unless synchronizeAnimatedSVGAttribute is called with
    // anyQName(). This means that even if Element::synchronizeAttribute()
    // is called on all attributes, m_animatedSVGAttributesAreDirty remains
    // true.
    toSVGElement(this)->synchronizeAnimatedSVGAttribute(
        QualifiedName(nullAtom, localName, nullAtom));
  }
}

const AtomicString& Element::getAttribute(const QualifiedName& name) const {
  if (!elementData())
    return nullAtom;
  synchronizeAttribute(name);
  if (const Attribute* attribute = elementData()->attributes().find(name))
    return attribute->value();
  return nullAtom;
}

bool Element::shouldIgnoreAttributeCase() const {
  return isHTMLElement() && document().isHTMLDocument();
}

void Element::scrollIntoView(bool alignToTop) {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (!layoutObject())
    return;

  bool makeVisibleInVisualViewport =
      !document().page()->settings().inertVisualViewport();

  LayoutRect bounds = boundingBox();
  // Align to the top / bottom and to the closest edge.
  if (alignToTop)
    layoutObject()->scrollRectToVisible(
        bounds, ScrollAlignment::alignToEdgeIfNeeded,
        ScrollAlignment::alignTopAlways, ProgrammaticScroll,
        makeVisibleInVisualViewport);
  else
    layoutObject()->scrollRectToVisible(
        bounds, ScrollAlignment::alignToEdgeIfNeeded,
        ScrollAlignment::alignBottomAlways, ProgrammaticScroll,
        makeVisibleInVisualViewport);

  document().setSequentialFocusNavigationStartingPoint(this);
}

void Element::scrollIntoViewIfNeeded(bool centerIfNeeded) {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (!layoutObject())
    return;

  bool makeVisibleInVisualViewport =
      !document().page()->settings().inertVisualViewport();

  LayoutRect bounds = boundingBox();
  if (centerIfNeeded)
    layoutObject()->scrollRectToVisible(
        bounds, ScrollAlignment::alignCenterIfNeeded,
        ScrollAlignment::alignCenterIfNeeded, ProgrammaticScroll,
        makeVisibleInVisualViewport);
  else
    layoutObject()->scrollRectToVisible(
        bounds, ScrollAlignment::alignToEdgeIfNeeded,
        ScrollAlignment::alignToEdgeIfNeeded, ProgrammaticScroll,
        makeVisibleInVisualViewport);
}

void Element::setDistributeScroll(ScrollStateCallback* scrollStateCallback,
                                  String nativeScrollBehavior) {
  scrollStateCallback->setNativeScrollBehavior(
      ScrollStateCallback::toNativeScrollBehavior(nativeScrollBehavior));
  scrollCustomizationCallbacks().setDistributeScroll(this, scrollStateCallback);
}

void Element::setApplyScroll(ScrollStateCallback* scrollStateCallback,
                             String nativeScrollBehavior) {
  scrollStateCallback->setNativeScrollBehavior(
      ScrollStateCallback::toNativeScrollBehavior(nativeScrollBehavior));
  scrollCustomizationCallbacks().setApplyScroll(this, scrollStateCallback);
}

void Element::removeApplyScroll() {
  scrollCustomizationCallbacks().removeApplyScroll(this);
}

ScrollStateCallback* Element::getApplyScroll() {
  return scrollCustomizationCallbacks().getApplyScroll(this);
}

void Element::nativeDistributeScroll(ScrollState& scrollState) {
  if (scrollState.fullyConsumed())
    return;

  scrollState.distributeToScrollChainDescendant();

  // If the scroll doesn't propagate, and we're currently scrolling
  // an element other than this one, prevent the scroll from
  // propagating to this element.
  if (!scrollState.shouldPropagate() &&
      scrollState.deltaConsumedForScrollSequence() &&
      scrollState.currentNativeScrollingElement() != this) {
    return;
  }

  const double deltaX = scrollState.deltaX();
  const double deltaY = scrollState.deltaY();

  callApplyScroll(scrollState);

  if (deltaX != scrollState.deltaX() || deltaY != scrollState.deltaY())
    scrollState.setCurrentNativeScrollingElement(this);
}

void Element::callDistributeScroll(ScrollState& scrollState) {
  ScrollStateCallback* callback =
      scrollCustomizationCallbacks().getDistributeScroll(this);

  // TODO(bokan): Need to add tests before we allow calling custom callbacks
  // for non-touch modalities. For now, just call into the native callback but
  // allow the viewport scroll callback so we don't disable overscroll.
  // crbug.com/623079.
  bool disableCustomCallbacks = !scrollState.isDirectManipulation() &&
                                !document()
                                     .frameHost()
                                     ->globalRootScrollerController()
                                     .isViewportScrollCallback(callback);

  if (!callback || disableCustomCallbacks) {
    nativeDistributeScroll(scrollState);
    return;
  }
  if (callback->nativeScrollBehavior() !=
      WebNativeScrollBehavior::PerformAfterNativeScroll)
    callback->handleEvent(&scrollState);
  if (callback->nativeScrollBehavior() !=
      WebNativeScrollBehavior::DisableNativeScroll)
    nativeDistributeScroll(scrollState);
  if (callback->nativeScrollBehavior() ==
      WebNativeScrollBehavior::PerformAfterNativeScroll)
    callback->handleEvent(&scrollState);
};

void Element::nativeApplyScroll(ScrollState& scrollState) {
  // All elements in the scroll chain should be boxes.
  DCHECK(!layoutObject() || layoutObject()->isBox());

  if (scrollState.fullyConsumed())
    return;

  FloatSize delta(scrollState.deltaX(), scrollState.deltaY());

  if (delta.isZero())
    return;

  // TODO(esprehn): This should use
  // updateStyleAndLayoutIgnorePendingStylesheetsForNode.
  document().updateStyleAndLayoutIgnorePendingStylesheets();

  LayoutBox* boxToScroll = nullptr;

  // We should only ever scroll the effective root scroller this way when the
  // page removes the default applyScroll (ViewportScrollCallback).
  if (document().rootScrollerController()->effectiveRootScroller() == this)
    boxToScroll = document().layoutView();
  else if (layoutObject())
    boxToScroll = toLayoutBox(layoutObject());

  if (!boxToScroll)
    return;

  ScrollResult result = LayoutBoxItem(boxToScroll)
                            .enclosingBox()
                            .scroll(ScrollGranularity(static_cast<int>(
                                        scrollState.deltaGranularity())),
                                    delta);

  if (!result.didScroll())
    return;

  // FIXME: Native scrollers should only consume the scroll they
  // apply. See crbug.com/457765.
  scrollState.consumeDeltaNative(delta.width(), delta.height());

  // We need to setCurrentNativeScrollingElement in both the
  // distributeScroll and applyScroll default implementations so
  // that if JS overrides one of these methods, but not the
  // other, this bookkeeping remains accurate.
  scrollState.setCurrentNativeScrollingElement(this);
  if (scrollState.fromUserInput()) {
    if (DocumentLoader* documentLoader = document().loader())
      documentLoader->initialScrollState().wasScrolledByUser = true;
  }
};

void Element::callApplyScroll(ScrollState& scrollState) {
  // Hits ASSERTs when trying to determine whether we need to scroll on main
  // or CC. http://crbug.com/625676.
  DisableCompositingQueryAsserts disabler;

  ScrollStateCallback* callback =
      scrollCustomizationCallbacks().getApplyScroll(this);

  // TODO(bokan): Need to add tests before we allow calling custom callbacks
  // for non-touch modalities. For now, just call into the native callback but
  // allow the viewport scroll callback so we don't disable overscroll.
  // crbug.com/623079.
  bool disableCustomCallbacks = !scrollState.isDirectManipulation() &&
                                !document()
                                     .frameHost()
                                     ->globalRootScrollerController()
                                     .isViewportScrollCallback(callback);

  if (!callback || disableCustomCallbacks) {
    nativeApplyScroll(scrollState);
    return;
  }
  if (callback->nativeScrollBehavior() !=
      WebNativeScrollBehavior::PerformAfterNativeScroll)
    callback->handleEvent(&scrollState);
  if (callback->nativeScrollBehavior() !=
      WebNativeScrollBehavior::DisableNativeScroll)
    nativeApplyScroll(scrollState);
  if (callback->nativeScrollBehavior() ==
      WebNativeScrollBehavior::PerformAfterNativeScroll)
    callback->handleEvent(&scrollState);
}

int Element::offsetLeft() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);
  if (LayoutBoxModelObject* layoutObject = layoutBoxModelObject())
    return adjustLayoutUnitForAbsoluteZoom(
               LayoutUnit(layoutObject->pixelSnappedOffsetLeft(offsetParent())),
               layoutObject->styleRef())
        .round();
  return 0;
}

int Element::offsetTop() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);
  if (LayoutBoxModelObject* layoutObject = layoutBoxModelObject())
    return adjustLayoutUnitForAbsoluteZoom(
               LayoutUnit(layoutObject->pixelSnappedOffsetTop(offsetParent())),
               layoutObject->styleRef())
        .round();
  return 0;
}

int Element::offsetWidth() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);
  if (LayoutBoxModelObject* layoutObject = layoutBoxModelObject())
    return adjustLayoutUnitForAbsoluteZoom(
               LayoutUnit(
                   layoutObject->pixelSnappedOffsetWidth(offsetParent())),
               layoutObject->styleRef())
        .round();
  return 0;
}

int Element::offsetHeight() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);
  if (LayoutBoxModelObject* layoutObject = layoutBoxModelObject())
    return adjustLayoutUnitForAbsoluteZoom(
               LayoutUnit(
                   layoutObject->pixelSnappedOffsetHeight(offsetParent())),
               layoutObject->styleRef())
        .round();
  return 0;
}

Element* Element::offsetParent() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  LayoutObject* layoutObject = this->layoutObject();
  return layoutObject ? layoutObject->offsetParent() : nullptr;
}

int Element::clientLeft() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (LayoutBox* layoutObject = layoutBox())
    return adjustLayoutUnitForAbsoluteZoom(layoutObject->clientLeft(),
                                           layoutObject->styleRef())
        .round();
  return 0;
}

int Element::clientTop() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (LayoutBox* layoutObject = layoutBox())
    return adjustLayoutUnitForAbsoluteZoom(layoutObject->clientTop(),
                                           layoutObject->styleRef())
        .round();
  return 0;
}

int Element::clientWidth() {
  // When in strict mode, clientWidth for the document element should return the
  // width of the containing frame.
  // When in quirks mode, clientWidth for the body element should return the
  // width of the containing frame.
  bool inQuirksMode = document().inQuirksMode();
  if ((!inQuirksMode && document().documentElement() == this) ||
      (inQuirksMode && isHTMLElement() && document().body() == this)) {
    LayoutViewItem layoutView = document().layoutViewItem();
    if (!layoutView.isNull()) {
      if (!RuntimeEnabledFeatures::overlayScrollbarsEnabled() ||
          !document().frame()->isLocalRoot())
        document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);
      if (document().page()->settings().forceZeroLayoutHeight())
        return adjustLayoutUnitForAbsoluteZoom(
                   layoutView.overflowClipRect(LayoutPoint()).width(),
                   layoutView.styleRef())
            .round();
      return adjustLayoutUnitForAbsoluteZoom(
                 LayoutUnit(layoutView.layoutSize().width()),
                 layoutView.styleRef())
          .round();
    }
  }

  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (LayoutBox* layoutObject = layoutBox())
    return adjustLayoutUnitForAbsoluteZoom(
               LayoutUnit(layoutObject->pixelSnappedClientWidth()),
               layoutObject->styleRef())
        .round();
  return 0;
}

int Element::clientHeight() {
  // When in strict mode, clientHeight for the document element should return
  // the height of the containing frame.
  // When in quirks mode, clientHeight for the body element should return the
  // height of the containing frame.
  bool inQuirksMode = document().inQuirksMode();

  if ((!inQuirksMode && document().documentElement() == this) ||
      (inQuirksMode && isHTMLElement() && document().body() == this)) {
    LayoutViewItem layoutView = document().layoutViewItem();
    if (!layoutView.isNull()) {
      if (!RuntimeEnabledFeatures::overlayScrollbarsEnabled() ||
          !document().frame()->isLocalRoot())
        document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);
      if (document().page()->settings().forceZeroLayoutHeight())
        return adjustLayoutUnitForAbsoluteZoom(
                   layoutView.overflowClipRect(LayoutPoint()).height(),
                   layoutView.styleRef())
            .round();
      return adjustLayoutUnitForAbsoluteZoom(
                 LayoutUnit(layoutView.layoutSize().height()),
                 layoutView.styleRef())
          .round();
    }
  }

  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (LayoutBox* layoutObject = layoutBox())
    return adjustLayoutUnitForAbsoluteZoom(
               LayoutUnit(layoutObject->pixelSnappedClientHeight()),
               layoutObject->styleRef())
        .round();
  return 0;
}

double Element::scrollLeft() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (document().scrollingElement() == this) {
    if (document().domWindow())
      return document().domWindow()->scrollX();
    return 0;
  }

  if (LayoutBox* box = layoutBox())
    return adjustScrollForAbsoluteZoom(box->scrollLeft(), *box);

  return 0;
}

double Element::scrollTop() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (document().scrollingElement() == this) {
    if (document().domWindow())
      return document().domWindow()->scrollY();
    return 0;
  }

  if (LayoutBox* box = layoutBox())
    return adjustScrollForAbsoluteZoom(box->scrollTop(), *box);

  return 0;
}

void Element::setScrollLeft(double newLeft) {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  newLeft = ScrollableArea::normalizeNonFiniteScroll(newLeft);

  if (document().scrollingElement() == this) {
    if (LocalDOMWindow* window = document().domWindow())
      window->scrollTo(newLeft, window->scrollY());
  } else {
    LayoutBox* box = layoutBox();
    if (box)
      box->setScrollLeft(
          LayoutUnit::fromFloatRound(newLeft * box->style()->effectiveZoom()));
  }
}

void Element::setScrollTop(double newTop) {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  newTop = ScrollableArea::normalizeNonFiniteScroll(newTop);

  if (document().scrollingElement() == this) {
    if (LocalDOMWindow* window = document().domWindow())
      window->scrollTo(window->scrollX(), newTop);
  } else {
    LayoutBox* box = layoutBox();
    if (box)
      box->setScrollTop(
          LayoutUnit::fromFloatRound(newTop * box->style()->effectiveZoom()));
  }
}

int Element::scrollWidth() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (document().scrollingElement() == this) {
    if (document().view())
      return adjustForAbsoluteZoom(document().view()->contentsWidth(),
                                   document().frame()->pageZoomFactor());
    return 0;
  }

  if (LayoutBox* box = layoutBox())
    return adjustForAbsoluteZoom(box->pixelSnappedScrollWidth(), box);
  return 0;
}

int Element::scrollHeight() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (document().scrollingElement() == this) {
    if (document().view())
      return adjustForAbsoluteZoom(document().view()->contentsHeight(),
                                   document().frame()->pageZoomFactor());
    return 0;
  }

  if (LayoutBox* box = layoutBox())
    return adjustForAbsoluteZoom(box->pixelSnappedScrollHeight(), box);
  return 0;
}

void Element::scrollBy(double x, double y) {
  ScrollToOptions scrollToOptions;
  scrollToOptions.setLeft(x);
  scrollToOptions.setTop(y);
  scrollBy(scrollToOptions);
}

void Element::scrollBy(const ScrollToOptions& scrollToOptions) {
  // FIXME: This should be removed once scroll updates are processed only after
  // the compositing update. See http://crbug.com/420741.
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (document().scrollingElement() == this) {
    scrollFrameBy(scrollToOptions);
  } else {
    scrollLayoutBoxBy(scrollToOptions);
  }
}

void Element::scrollTo(double x, double y) {
  ScrollToOptions scrollToOptions;
  scrollToOptions.setLeft(x);
  scrollToOptions.setTop(y);
  scrollTo(scrollToOptions);
}

void Element::scrollTo(const ScrollToOptions& scrollToOptions) {
  // FIXME: This should be removed once scroll updates are processed only after
  // the compositing update. See http://crbug.com/420741.
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (document().scrollingElement() == this) {
    scrollFrameTo(scrollToOptions);
  } else {
    scrollLayoutBoxTo(scrollToOptions);
  }
}

void Element::scrollLayoutBoxBy(const ScrollToOptions& scrollToOptions) {
  double left =
      scrollToOptions.hasLeft()
          ? ScrollableArea::normalizeNonFiniteScroll(scrollToOptions.left())
          : 0.0;
  double top =
      scrollToOptions.hasTop()
          ? ScrollableArea::normalizeNonFiniteScroll(scrollToOptions.top())
          : 0.0;

  ScrollBehavior scrollBehavior = ScrollBehaviorAuto;
  ScrollableArea::scrollBehaviorFromString(scrollToOptions.behavior(),
                                           scrollBehavior);
  LayoutBox* box = layoutBox();
  if (box) {
    double currentScaledLeft = box->scrollLeft();
    double currentScaledTop = box->scrollTop();
    double newScaledLeft =
        left * box->style()->effectiveZoom() + currentScaledLeft;
    double newScaledTop =
        top * box->style()->effectiveZoom() + currentScaledTop;
    box->scrollToOffset(DoubleSize(newScaledLeft, newScaledTop),
                        scrollBehavior);
  }
}

void Element::scrollLayoutBoxTo(const ScrollToOptions& scrollToOptions) {
  ScrollBehavior scrollBehavior = ScrollBehaviorAuto;
  ScrollableArea::scrollBehaviorFromString(scrollToOptions.behavior(),
                                           scrollBehavior);

  LayoutBox* box = layoutBox();
  if (box) {
    double scaledLeft = box->scrollLeft();
    double scaledTop = box->scrollTop();
    if (scrollToOptions.hasLeft())
      scaledLeft =
          ScrollableArea::normalizeNonFiniteScroll(scrollToOptions.left()) *
          box->style()->effectiveZoom();
    if (scrollToOptions.hasTop())
      scaledTop =
          ScrollableArea::normalizeNonFiniteScroll(scrollToOptions.top()) *
          box->style()->effectiveZoom();
    box->scrollToOffset(DoubleSize(scaledLeft, scaledTop), scrollBehavior);
  }
}

void Element::scrollFrameBy(const ScrollToOptions& scrollToOptions) {
  double left =
      scrollToOptions.hasLeft()
          ? ScrollableArea::normalizeNonFiniteScroll(scrollToOptions.left())
          : 0.0;
  double top =
      scrollToOptions.hasTop()
          ? ScrollableArea::normalizeNonFiniteScroll(scrollToOptions.top())
          : 0.0;

  ScrollBehavior scrollBehavior = ScrollBehaviorAuto;
  ScrollableArea::scrollBehaviorFromString(scrollToOptions.behavior(),
                                           scrollBehavior);
  LocalFrame* frame = document().frame();
  if (!frame)
    return;
  ScrollableArea* viewport =
      frame->view() ? frame->view()->getScrollableArea() : 0;
  if (!viewport)
    return;

  double newScaledLeft =
      left * frame->pageZoomFactor() + viewport->scrollPositionDouble().x();
  double newScaledTop =
      top * frame->pageZoomFactor() + viewport->scrollPositionDouble().y();
  viewport->setScrollPosition(DoublePoint(newScaledLeft, newScaledTop),
                              ProgrammaticScroll, scrollBehavior);
}

void Element::scrollFrameTo(const ScrollToOptions& scrollToOptions) {
  ScrollBehavior scrollBehavior = ScrollBehaviorAuto;
  ScrollableArea::scrollBehaviorFromString(scrollToOptions.behavior(),
                                           scrollBehavior);
  LocalFrame* frame = document().frame();
  if (!frame)
    return;
  ScrollableArea* viewport =
      frame->view() ? frame->view()->getScrollableArea() : 0;
  if (!viewport)
    return;

  double scaledLeft = viewport->scrollPositionDouble().x();
  double scaledTop = viewport->scrollPositionDouble().y();
  if (scrollToOptions.hasLeft())
    scaledLeft =
        ScrollableArea::normalizeNonFiniteScroll(scrollToOptions.left()) *
        frame->pageZoomFactor();
  if (scrollToOptions.hasTop())
    scaledTop =
        ScrollableArea::normalizeNonFiniteScroll(scrollToOptions.top()) *
        frame->pageZoomFactor();
  viewport->setScrollPosition(DoublePoint(scaledLeft, scaledTop),
                              ProgrammaticScroll, scrollBehavior);
}

bool Element::hasCompositorProxy() const {
  return hasRareData() && elementRareData()->proxiedPropertyCounts();
}

void Element::incrementCompositorProxiedProperties(uint32_t mutableProperties) {
  ElementRareData& rareData = ensureElementRareData();
  if (!rareData.proxiedPropertyCounts())
    setNeedsStyleRecalc(LocalStyleChange,
                        StyleChangeReasonForTracing::create(
                            StyleChangeReason::CompositorProxy));
  rareData.incrementCompositorProxiedProperties(mutableProperties);
}

void Element::decrementCompositorProxiedProperties(uint32_t mutableProperties) {
  ElementRareData& rareData = *elementRareData();
  rareData.decrementCompositorProxiedProperties(mutableProperties);
  if (!rareData.proxiedPropertyCounts())
    setNeedsStyleRecalc(LocalStyleChange,
                        StyleChangeReasonForTracing::create(
                            StyleChangeReason::CompositorProxy));
}

void Element::updateFromCompositorMutation(const CompositorMutation& mutation) {
  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("compositor-worker"),
               "Element::updateFromCompositorMutation");
  if (mutation.isOpacityMutated() || mutation.isTransformMutated())
    ensureElementAnimations().customCompositorAnimations().applyUpdate(
        *this, mutation);
}

uint32_t Element::compositorMutableProperties() const {
  if (!hasRareData())
    return CompositorMutableProperty::kNone;
  if (CompositorProxiedPropertySet* set =
          elementRareData()->proxiedPropertyCounts())
    return set->proxiedProperties();
  return CompositorMutableProperty::kNone;
}

bool Element::hasNonEmptyLayoutSize() const {
  document().updateStyleAndLayoutIgnorePendingStylesheets();

  if (LayoutBoxModelObject* box = layoutBoxModelObject())
    return box->hasNonEmptyLayoutSize();
  return false;
}

IntRect Element::boundsInViewport() const {
  document().updateStyleAndLayoutIgnorePendingStylesheets();

  FrameView* view = document().view();
  if (!view)
    return IntRect();

  Vector<FloatQuad> quads;
  if (isSVGElement() && layoutObject()) {
    // Get the bounding rectangle from the SVG model.
    if (toSVGElement(this)->isSVGGraphicsElement())
      quads.append(layoutObject()->localToAbsoluteQuad(
          layoutObject()->objectBoundingBox()));
  } else {
    // Get the bounding rectangle from the box model.
    if (layoutBoxModelObject())
      layoutBoxModelObject()->absoluteQuads(quads);
  }

  if (quads.isEmpty())
    return IntRect();

  IntRect result = quads[0].enclosingBoundingBox();
  for (size_t i = 1; i < quads.size(); ++i)
    result.unite(quads[i].enclosingBoundingBox());

  return view->contentsToViewport(result);
}

IntRect Element::visibleBoundsInVisualViewport() const {
  if (!layoutObject() || !document().page())
    return IntRect();
  // TODO(tkent): Can we check invisibility by scrollable non-frame elements?

  IntSize viewportSize = document().page()->frameHost().visualViewport().size();
  IntRect rect(0, 0, viewportSize.width(), viewportSize.height());
  // We don't use absoluteBoundingBoxRect() because it can return an IntRect
  // larger the actual size by 1px. crbug.com/470503
  rect.intersect(document().view()->contentsToViewport(
      roundedIntRect(layoutObject()->absoluteBoundingBoxFloatRect())));
  return rect;
}

void Element::clientQuads(Vector<FloatQuad>& quads) {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  LayoutObject* elementLayoutObject = layoutObject();
  if (!elementLayoutObject)
    return;

  if (isSVGElement() && !elementLayoutObject->isSVGRoot()) {
    // Get the bounding rectangle from the SVG model.
    if (toSVGElement(this)->isSVGGraphicsElement())
      quads.append(elementLayoutObject->localToAbsoluteQuad(
          elementLayoutObject->objectBoundingBox()));
    return;
  }

  // FIXME: Handle table/inline-table with a caption.
  if (elementLayoutObject->isBoxModelObject() || elementLayoutObject->isBR())
    elementLayoutObject->absoluteQuads(quads);
}

ClientRectList* Element::getClientRects() {
  Vector<FloatQuad> quads;
  clientQuads(quads);
  if (quads.isEmpty())
    return ClientRectList::create();

  LayoutObject* elementLayoutObject = layoutObject();
  DCHECK(elementLayoutObject);
  document().adjustFloatQuadsForScrollAndAbsoluteZoom(quads,
                                                      *elementLayoutObject);
  return ClientRectList::create(quads);
}

ClientRect* Element::getBoundingClientRect() {
  Vector<FloatQuad> quads;
  clientQuads(quads);
  if (quads.isEmpty())
    return ClientRect::create();

  FloatRect result = quads[0].boundingBox();
  for (size_t i = 1; i < quads.size(); ++i)
    result.unite(quads[i].boundingBox());

  LayoutObject* elementLayoutObject = layoutObject();
  DCHECK(elementLayoutObject);
  document().adjustFloatRectForScrollAndAbsoluteZoom(result,
                                                     *elementLayoutObject);
  return ClientRect::create(result);
}

const AtomicString& Element::computedRole() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);
  std::unique_ptr<ScopedAXObjectCache> cache =
      ScopedAXObjectCache::create(document());
  return cache->get()->computedRoleForNode(this);
}

String Element::computedName() {
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);
  std::unique_ptr<ScopedAXObjectCache> cache =
      ScopedAXObjectCache::create(document());
  return cache->get()->computedNameForNode(this);
}

const AtomicString& Element::getAttribute(const AtomicString& localName) const {
  if (!elementData())
    return nullAtom;
  synchronizeAttribute(localName);
  if (const Attribute* attribute = elementData()->attributes().find(
          localName, shouldIgnoreAttributeCase()))
    return attribute->value();
  return nullAtom;
}

const AtomicString& Element::getAttributeNS(
    const AtomicString& namespaceURI,
    const AtomicString& localName) const {
  return getAttribute(QualifiedName(nullAtom, localName, namespaceURI));
}

void Element::setAttribute(const AtomicString& localName,
                           const AtomicString& value,
                           ExceptionState& exceptionState) {
  if (!Document::isValidName(localName)) {
    exceptionState.throwDOMException(
        InvalidCharacterError,
        "'" + localName + "' is not a valid attribute name.");
    return;
  }

  synchronizeAttribute(localName);
  const AtomicString& caseAdjustedLocalName =
      shouldIgnoreAttributeCase() ? localName.lower() : localName;

  if (!elementData()) {
    setAttributeInternal(
        kNotFound, QualifiedName(nullAtom, caseAdjustedLocalName, nullAtom),
        value, NotInSynchronizationOfLazyAttribute);
    return;
  }

  AttributeCollection attributes = elementData()->attributes();
  size_t index = attributes.findIndex(caseAdjustedLocalName, false);
  const QualifiedName& qName =
      index != kNotFound
          ? attributes[index].name()
          : QualifiedName(nullAtom, caseAdjustedLocalName, nullAtom);
  setAttributeInternal(index, qName, value,
                       NotInSynchronizationOfLazyAttribute);
}

void Element::setAttribute(const QualifiedName& name,
                           const AtomicString& value) {
  synchronizeAttribute(name);
  size_t index =
      elementData() ? elementData()->attributes().findIndex(name) : kNotFound;
  setAttributeInternal(index, name, value, NotInSynchronizationOfLazyAttribute);
}

void Element::setSynchronizedLazyAttribute(const QualifiedName& name,
                                           const AtomicString& value) {
  size_t index =
      elementData() ? elementData()->attributes().findIndex(name) : kNotFound;
  setAttributeInternal(index, name, value, InSynchronizationOfLazyAttribute);
}

ALWAYS_INLINE void Element::setAttributeInternal(
    size_t index,
    const QualifiedName& name,
    const AtomicString& newValue,
    SynchronizationOfLazyAttribute inSynchronizationOfLazyAttribute) {
  if (newValue.isNull()) {
    if (index != kNotFound)
      removeAttributeInternal(index, inSynchronizationOfLazyAttribute);
    return;
  }

  if (index == kNotFound) {
    appendAttributeInternal(name, newValue, inSynchronizationOfLazyAttribute);
    return;
  }

  const Attribute& existingAttribute = elementData()->attributes().at(index);
  AtomicString existingAttributeValue = existingAttribute.value();
  QualifiedName existingAttributeName = existingAttribute.name();

  if (!inSynchronizationOfLazyAttribute)
    willModifyAttribute(existingAttributeName, existingAttributeValue,
                        newValue);
  if (newValue != existingAttributeValue)
    ensureUniqueElementData().attributes().at(index).setValue(newValue);
  if (!inSynchronizationOfLazyAttribute)
    didModifyAttribute(existingAttributeName, existingAttributeValue, newValue);
}

static inline AtomicString makeIdForStyleResolution(const AtomicString& value,
                                                    bool inQuirksMode) {
  if (inQuirksMode)
    return value.lowerASCII();
  return value;
}

DISABLE_CFI_PERF
void Element::attributeChanged(const QualifiedName& name,
                               const AtomicString& oldValue,
                               const AtomicString& newValue,
                               AttributeModificationReason reason) {
  if (ElementShadow* parentElementShadow =
          shadowWhereNodeCanBeDistributedForV0(*this)) {
    if (shouldInvalidateDistributionWhenAttributeChanged(parentElementShadow,
                                                         name, newValue))
      parentElementShadow->setNeedsDistributionRecalc();
  }
  if (name == HTMLNames::slotAttr && oldValue != newValue) {
    if (ShadowRoot* root = v1ShadowRootOfParent())
      root->ensureSlotAssignment().hostChildSlotNameChanged(oldValue, newValue);
  }

  parseAttribute(name, oldValue, newValue);

  document().incDOMTreeVersion();

  if (name == HTMLNames::idAttr) {
    AtomicString oldId = elementData()->idForStyleResolution();
    AtomicString newId =
        makeIdForStyleResolution(newValue, document().inQuirksMode());
    if (newId != oldId) {
      elementData()->setIdForStyleResolution(newId);
      document().styleEngine().idChangedForElement(oldId, newId, *this);
    }
  } else if (name == classAttr) {
    classAttributeChanged(newValue);
  } else if (name == HTMLNames::nameAttr) {
    setHasName(!newValue.isNull());
  } else if (isStyledElement()) {
    if (name == styleAttr) {
      styleAttributeChanged(newValue, reason);
    } else if (isPresentationAttribute(name)) {
      elementData()->m_presentationAttributeStyleIsDirty = true;
      setNeedsStyleRecalc(LocalStyleChange,
                          StyleChangeReasonForTracing::fromAttribute(name));
    }
  }

  invalidateNodeListCachesInAncestors(&name, this);

  // If there is currently no StyleResolver, we can't be sure that this
  // attribute change won't affect style.
  if (!document().styleResolver())
    setNeedsStyleRecalc(SubtreeStyleChange,
                        StyleChangeReasonForTracing::fromAttribute(name));

  if (isConnected()) {
    if (AXObjectCache* cache = document().existingAXObjectCache())
      cache->handleAttributeChanged(name, this);
  }
}

bool Element::hasLegalLinkAttribute(const QualifiedName&) const {
  return false;
}

const QualifiedName& Element::subResourceAttributeName() const {
  return QualifiedName::null();
}

inline void Element::attributeChangedFromParserOrByCloning(
    const QualifiedName& name,
    const AtomicString& newValue,
    AttributeModificationReason reason) {
  if (name == isAttr)
    V0CustomElementRegistrationContext::setTypeExtension(this, newValue);
  attributeChanged(name, nullAtom, newValue, reason);
}

template <typename CharacterType>
static inline ClassStringContent classStringHasClassName(
    const CharacterType* characters,
    unsigned length) {
  DCHECK_GT(length, 0u);

  unsigned i = 0;
  do {
    if (isNotHTMLSpace<CharacterType>(characters[i]))
      break;
    ++i;
  } while (i < length);

  if (i == length && length == 1)
    return ClassStringContent::Empty;
  if (i == length && length > 1)
    return ClassStringContent::WhiteSpaceOnly;

  return ClassStringContent::HasClasses;
}

static inline ClassStringContent classStringHasClassName(
    const AtomicString& newClassString) {
  unsigned length = newClassString.length();

  if (!length)
    return ClassStringContent::Empty;

  if (newClassString.is8Bit())
    return classStringHasClassName(newClassString.characters8(), length);
  return classStringHasClassName(newClassString.characters16(), length);
}

void Element::classAttributeChanged(const AtomicString& newClassString) {
  DCHECK(elementData());
  ClassStringContent classStringContentType =
      classStringHasClassName(newClassString);
  const bool shouldFoldCase = document().inQuirksMode();
  if (classStringContentType == ClassStringContent::HasClasses) {
    const SpaceSplitString oldClasses = elementData()->classNames();
    elementData()->setClass(newClassString, shouldFoldCase);
    const SpaceSplitString& newClasses = elementData()->classNames();
    document().styleEngine().classChangedForElement(oldClasses, newClasses,
                                                    *this);
  } else {
    const SpaceSplitString& oldClasses = elementData()->classNames();
    document().styleEngine().classChangedForElement(oldClasses, *this);
    if (classStringContentType == ClassStringContent::WhiteSpaceOnly)
      elementData()->setClass(newClassString, shouldFoldCase);
    else
      elementData()->clearClass();
  }

  if (hasRareData())
    elementRareData()->clearClassListValueForQuirksMode();
}

bool Element::shouldInvalidateDistributionWhenAttributeChanged(
    ElementShadow* elementShadow,
    const QualifiedName& name,
    const AtomicString& newValue) {
  DCHECK(elementShadow);
  if (elementShadow->isV1())
    return false;
  const SelectRuleFeatureSet& featureSet =
      elementShadow->v0().ensureSelectFeatureSet();

  if (name == HTMLNames::idAttr) {
    AtomicString oldId = elementData()->idForStyleResolution();
    AtomicString newId =
        makeIdForStyleResolution(newValue, document().inQuirksMode());
    if (newId != oldId) {
      if (!oldId.isEmpty() && featureSet.hasSelectorForId(oldId))
        return true;
      if (!newId.isEmpty() && featureSet.hasSelectorForId(newId))
        return true;
    }
  }

  if (name == HTMLNames::classAttr) {
    const AtomicString& newClassString = newValue;
    if (classStringHasClassName(newClassString) ==
        ClassStringContent::HasClasses) {
      const SpaceSplitString& oldClasses = elementData()->classNames();
      const SpaceSplitString newClasses(
          newClassString, document().inQuirksMode()
                              ? SpaceSplitString::ShouldFoldCase
                              : SpaceSplitString::ShouldNotFoldCase);
      if (featureSet.checkSelectorsForClassChange(oldClasses, newClasses))
        return true;
    } else {
      const SpaceSplitString& oldClasses = elementData()->classNames();
      if (featureSet.checkSelectorsForClassChange(oldClasses))
        return true;
    }
  }

  return featureSet.hasSelectorForAttribute(name.localName());
}

// Returns true is the given attribute is an event handler.
// We consider an event handler any attribute that begins with "on".
// It is a simple solution that has the advantage of not requiring any
// code or configuration change if a new event handler is defined.

static inline bool isEventHandlerAttribute(const Attribute& attribute) {
  return attribute.name().namespaceURI().isNull() &&
         attribute.name().localName().startsWith("on");
}

bool Element::attributeValueIsJavaScriptURL(const Attribute& attribute) {
  return protocolIsJavaScript(
      stripLeadingAndTrailingHTMLSpaces(attribute.value()));
}

bool Element::isJavaScriptURLAttribute(const Attribute& attribute) const {
  return isURLAttribute(attribute) && attributeValueIsJavaScriptURL(attribute);
}

void Element::stripScriptingAttributes(
    Vector<Attribute>& attributeVector) const {
  size_t destination = 0;
  for (size_t source = 0; source < attributeVector.size(); ++source) {
    if (isEventHandlerAttribute(attributeVector[source]) ||
        isJavaScriptURLAttribute(attributeVector[source]) ||
        isHTMLContentAttribute(attributeVector[source]) ||
        isSVGAnimationAttributeSettingJavaScriptURL(attributeVector[source]))
      continue;

    if (source != destination)
      attributeVector[destination] = attributeVector[source];

    ++destination;
  }
  attributeVector.shrink(destination);
}

void Element::parserSetAttributes(const Vector<Attribute>& attributeVector) {
  DCHECK(!isConnected());
  DCHECK(!parentNode());
  DCHECK(!m_elementData);

  if (!attributeVector.isEmpty()) {
    if (document().elementDataCache())
      m_elementData =
          document()
              .elementDataCache()
              ->cachedShareableElementDataWithAttributes(attributeVector);
    else
      m_elementData =
          ShareableElementData::createWithAttributes(attributeVector);
  }

  parserDidSetAttributes();

  // Use attributeVector instead of m_elementData because attributeChanged might
  // modify m_elementData.
  for (const auto& attribute : attributeVector)
    attributeChangedFromParserOrByCloning(attribute.name(), attribute.value(),
                                          ModifiedDirectly);
}

bool Element::hasEquivalentAttributes(const Element* other) const {
  synchronizeAllAttributes();
  other->synchronizeAllAttributes();
  if (elementData() == other->elementData())
    return true;
  if (elementData())
    return elementData()->isEquivalent(other->elementData());
  if (other->elementData())
    return other->elementData()->isEquivalent(elementData());
  return true;
}

String Element::nodeName() const {
  return m_tagName.toString();
}

const AtomicString& Element::locateNamespacePrefix(
    const AtomicString& namespaceToLocate) const {
  if (!prefix().isNull() && namespaceURI() == namespaceToLocate)
    return prefix();

  AttributeCollection attributes = this->attributes();
  for (const Attribute& attr : attributes) {
    if (attr.prefix() == xmlnsAtom && attr.value() == namespaceToLocate)
      return attr.localName();
  }

  if (Element* parent = parentElement())
    return parent->locateNamespacePrefix(namespaceToLocate);

  return nullAtom;
}

const AtomicString Element::imageSourceURL() const {
  return getAttribute(srcAttr);
}

bool Element::layoutObjectIsNeeded(const ComputedStyle& style) {
  return style.display() != EDisplay::None;
}

LayoutObject* Element::createLayoutObject(const ComputedStyle& style) {
  return LayoutObject::createObject(this, style);
}

Node::InsertionNotificationRequest Element::insertedInto(
    ContainerNode* insertionPoint) {
  // need to do superclass processing first so isConnected() is true
  // by the time we reach updateId
  ContainerNode::insertedInto(insertionPoint);

  if (containsFullScreenElement() && parentElement() &&
      !parentElement()->containsFullScreenElement())
    setContainsFullScreenElementOnAncestorsCrossingFrameBoundaries(true);

  DCHECK(!hasRareData() || !elementRareData()->hasPseudoElements());

  if (!insertionPoint->isInTreeScope())
    return InsertionDone;

  if (hasRareData()) {
    ElementRareData* rareData = elementRareData();
    rareData->clearClassListValueForQuirksMode();
    if (rareData->intersectionObserverData())
      rareData->intersectionObserverData()->activateValidIntersectionObservers(
          *this);
  }

  if (isConnected()) {
    if (getCustomElementState() == CustomElementState::Custom)
      CustomElement::enqueueConnectedCallback(this);
    else if (isUpgradedV0CustomElement())
      V0CustomElement::didAttach(this, document());
    else if (getCustomElementState() == CustomElementState::Undefined)
      CustomElement::tryToUpgrade(this);
  }

  TreeScope& scope = insertionPoint->treeScope();
  if (scope != treeScope())
    return InsertionDone;

  const AtomicString& idValue = getIdAttribute();
  if (!idValue.isNull())
    updateId(scope, nullAtom, idValue);

  const AtomicString& nameValue = getNameAttribute();
  if (!nameValue.isNull())
    updateName(nullAtom, nameValue);

  if (parentElement() && parentElement()->isInCanvasSubtree())
    setIsInCanvasSubtree(true);

  return InsertionDone;
}

void Element::removedFrom(ContainerNode* insertionPoint) {
  bool wasInDocument = insertionPoint->isConnected();

  DCHECK(!hasRareData() || !elementRareData()->hasPseudoElements());

  if (Fullscreen::isCurrentFullScreenElement(*this)) {
    setContainsFullScreenElementOnAncestorsCrossingFrameBoundaries(false);
    if (insertionPoint->isElementNode()) {
      toElement(insertionPoint)->setContainsFullScreenElement(false);
      toElement(insertionPoint)
          ->setContainsFullScreenElementOnAncestorsCrossingFrameBoundaries(
              false);
    }
  }

  if (Fullscreen* fullscreen = Fullscreen::fromIfExists(document()))
    fullscreen->elementRemoved(*this);

  if (document().page())
    document().page()->pointerLockController().elementRemoved(this);

  setSavedLayerScrollOffset(IntSize());

  if (insertionPoint->isInTreeScope() && treeScope() == document()) {
    const AtomicString& idValue = getIdAttribute();
    if (!idValue.isNull())
      updateId(insertionPoint->treeScope(), idValue, nullAtom);

    const AtomicString& nameValue = getNameAttribute();
    if (!nameValue.isNull())
      updateName(nameValue, nullAtom);
  }

  ContainerNode::removedFrom(insertionPoint);
  if (wasInDocument) {
    if (this == document().cssTarget())
      document().setCSSTarget(nullptr);

    if (hasPendingResources())
      document().accessSVGExtensions().removeElementFromPendingResources(this);

    if (getCustomElementState() == CustomElementState::Custom)
      CustomElement::enqueueDisconnectedCallback(this);
    else if (isUpgradedV0CustomElement())
      V0CustomElement::didDetach(this, insertionPoint->document());

    if (needsStyleInvalidation())
      document().styleEngine().styleInvalidator().clearInvalidation(*this);
  }

  document().removeFromTopLayer(this);

  clearElementFlag(IsInCanvasSubtree);

  if (hasRareData()) {
    ElementRareData* data = elementRareData();

    data->clearRestyleFlags();

    if (ElementAnimations* elementAnimations = data->elementAnimations())
      elementAnimations->cssAnimations().cancel();

    if (data->intersectionObserverData())
      data->intersectionObserverData()->deactivateAllIntersectionObservers(
          *this);
  }

  if (document().frame())
    document().frame()->eventHandler().elementRemoved(this);
}

void Element::attachLayoutTree(const AttachContext& context) {
  DCHECK(document().inStyleRecalc());

  // We've already been through detach when doing an attach, but we might
  // need to clear any state that's been added since then.
  if (hasRareData() && getStyleChangeType() == NeedsReattachStyleChange) {
    ElementRareData* data = elementRareData();
    data->clearComputedStyle();
  }

  if (!isSlotOrActiveInsertionPoint())
    LayoutTreeBuilderForElement(*this, context.resolvedStyle)
        .createLayoutObjectIfNeeded();

  addCallbackSelectors();

  if (hasRareData() && !layoutObject()) {
    if (ElementAnimations* elementAnimations =
            elementRareData()->elementAnimations()) {
      elementAnimations->cssAnimations().cancel();
      elementAnimations->setAnimationStyleChange(false);
    }
  }

  SelectorFilterParentScope filterScope(*this);
  StyleSharingDepthScope sharingScope(*this);

  createPseudoElementIfNeeded(PseudoIdBefore);

  // When a shadow root exists, it does the work of attaching the children.
  if (ElementShadow* shadow = this->shadow())
    shadow->attach(context);

  ContainerNode::attachLayoutTree(context);

  createPseudoElementIfNeeded(PseudoIdAfter);
  createPseudoElementIfNeeded(PseudoIdBackdrop);

  // We create the first-letter element after the :before, :after and
  // children are attached because the first letter text could come
  // from any of them.
  createPseudoElementIfNeeded(PseudoIdFirstLetter);
}

void Element::detachLayoutTree(const AttachContext& context) {
  HTMLFrameOwnerElement::UpdateSuspendScope suspendWidgetHierarchyUpdates;
  cancelFocusAppearanceUpdate();
  removeCallbackSelectors();
  if (hasRareData()) {
    ElementRareData* data = elementRareData();
    data->clearPseudoElements();

    // attachLayoutTree() will clear the computed style for us when inside
    // recalcStyle.
    if (!document().inStyleRecalc())
      data->clearComputedStyle();

    if (ElementAnimations* elementAnimations = data->elementAnimations()) {
      if (context.performingReattach) {
        // FIXME: We call detach from within style recalc, so compositingState
        // is not up to date.
        // https://code.google.com/p/chromium/issues/detail?id=339847
        DisableCompositingQueryAsserts disabler;

        // FIXME: restart compositor animations rather than pull back to the
        // main thread
        elementAnimations->restartAnimationOnCompositor();
      } else {
        elementAnimations->cssAnimations().cancel();
        elementAnimations->setAnimationStyleChange(false);
      }
      elementAnimations->clearBaseComputedStyle();
    }

    if (ElementShadow* shadow = data->shadow())
      shadow->detach(context);
  }

  ContainerNode::detachLayoutTree(context);

  if (!context.performingReattach && isUserActionElement()) {
    if (hovered())
      document().hoveredNodeDetached(*this);
    if (inActiveChain())
      document().activeChainNodeDetached(*this);
    document().userActionElements().didDetach(*this);
  }

  if (context.clearInvalidation)
    document().styleEngine().styleInvalidator().clearInvalidation(*this);

  if (svgFilterNeedsLayerUpdate())
    document().unscheduleSVGFilterLayerUpdateHack(*this);

  setNeedsResizeObserverUpdate();

  DCHECK(needsAttach());
}

bool Element::pseudoStyleCacheIsInvalid(const ComputedStyle* currentStyle,
                                        ComputedStyle* newStyle) {
  DCHECK_EQ(currentStyle, computedStyle());
  DCHECK(layoutObject());

  if (!currentStyle)
    return false;

  const PseudoStyleCache* pseudoStyleCache = currentStyle->cachedPseudoStyles();
  if (!pseudoStyleCache)
    return false;

  size_t cacheSize = pseudoStyleCache->size();
  for (size_t i = 0; i < cacheSize; ++i) {
    RefPtr<ComputedStyle> newPseudoStyle;
    RefPtr<ComputedStyle> oldPseudoStyle = pseudoStyleCache->at(i);
    PseudoId pseudoId = oldPseudoStyle->styleType();
    if (pseudoId == PseudoIdFirstLine || pseudoId == PseudoIdFirstLineInherited)
      newPseudoStyle = layoutObject()->uncachedFirstLineStyle(newStyle);
    else
      newPseudoStyle = layoutObject()->getUncachedPseudoStyle(
          PseudoStyleRequest(pseudoId), newStyle, newStyle);
    if (!newPseudoStyle)
      return true;
    if (*oldPseudoStyle != *newPseudoStyle ||
        oldPseudoStyle->font().loadingCustomFonts() !=
            newPseudoStyle->font().loadingCustomFonts()) {
      if (pseudoId < FirstInternalPseudoId)
        newStyle->setHasPseudoStyle(pseudoId);
      newStyle->addCachedPseudoStyle(newPseudoStyle);
      if (pseudoId == PseudoIdFirstLine ||
          pseudoId == PseudoIdFirstLineInherited)
        layoutObject()->firstLineStyleDidChange(*oldPseudoStyle,
                                                *newPseudoStyle);
      return true;
    }
  }
  return false;
}

PassRefPtr<ComputedStyle> Element::styleForLayoutObject() {
  DCHECK(document().inStyleRecalc());

  RefPtr<ComputedStyle> style;

  // FIXME: Instead of clearing updates that may have been added from calls to
  // styleForElement outside recalcStyle, we should just never set them if we're
  // not inside recalcStyle.
  if (ElementAnimations* elementAnimations = this->elementAnimations())
    elementAnimations->cssAnimations().clearPendingUpdate();

  if (hasCustomStyleCallbacks())
    style = customStyleForLayoutObject();
  if (!style)
    style = originalStyleForLayoutObject();
  DCHECK(style);

  // styleForElement() might add active animations so we need to get it again.
  if (ElementAnimations* elementAnimations = this->elementAnimations()) {
    elementAnimations->cssAnimations().maybeApplyPendingUpdate(this);
    elementAnimations->updateAnimationFlags(*style);
  }

  if (style->hasTransform()) {
    if (const StylePropertySet* inlineStyle = this->inlineStyle())
      style->setHasInlineTransform(
          inlineStyle->hasProperty(CSSPropertyTransform));
  }

  style->updateIsStackingContext(this == document().documentElement(),
                                 isInTopLayer());

  return style.release();
}

PassRefPtr<ComputedStyle> Element::originalStyleForLayoutObject() {
  DCHECK(document().inStyleRecalc());
  return document().ensureStyleResolver().styleForElement(this);
}

void Element::recalcStyle(StyleRecalcChange change, Text* nextTextSibling) {
  DCHECK(document().inStyleRecalc());
  DCHECK(!document().lifecycle().inDetach());
  DCHECK(!parentOrShadowHostNode()->needsStyleRecalc());
  DCHECK(inActiveDocument());

  if (hasCustomStyleCallbacks())
    willRecalcStyle(change);

  if (change >= IndependentInherit || needsStyleRecalc()) {
    if (hasRareData()) {
      ElementRareData* data = elementRareData();
      if (change != IndependentInherit)
        data->clearComputedStyle();

      if (change >= IndependentInherit) {
        if (ElementAnimations* elementAnimations = data->elementAnimations())
          elementAnimations->setAnimationStyleChange(false);
      }
    }
    if (parentComputedStyle())
      change = recalcOwnStyle(change);
    clearNeedsStyleRecalc();
  }

  // If we reattached we don't need to recalc the style of our descendants
  // anymore.
  if ((change >= UpdatePseudoElements && change < Reattach) ||
      childNeedsStyleRecalc()) {
    SelectorFilterParentScope filterScope(*this);
    StyleSharingDepthScope sharingScope(*this);

    updatePseudoElement(PseudoIdBefore, change);

    if (change > UpdatePseudoElements || childNeedsStyleRecalc()) {
      for (ShadowRoot* root = youngestShadowRoot(); root;
           root = root->olderShadowRoot()) {
        if (root->shouldCallRecalcStyle(change))
          root->recalcStyle(change);
      }
      recalcDescendantStyles(change);
    }

    updatePseudoElement(PseudoIdAfter, change);
    updatePseudoElement(PseudoIdBackdrop, change);

    // If our children have changed then we need to force the first-letter
    // checks as we don't know if they effected the first letter or not.
    // This can be seen when a child transitions from floating to
    // non-floating we have to take it into account for the first letter.
    updatePseudoElement(PseudoIdFirstLetter,
                        childNeedsStyleRecalc() ? Force : change);

    clearChildNeedsStyleRecalc();
  }

  if (hasCustomStyleCallbacks())
    didRecalcStyle(change);

  if (change == Reattach)
    reattachWhitespaceSiblingsIfNeeded(nextTextSibling);
}

PassRefPtr<ComputedStyle> Element::propagateInheritedProperties(
    StyleRecalcChange change) {
  if (change != IndependentInherit)
    return nullptr;
  if (needsStyleRecalc())
    return nullptr;
  if (hasAnimations())
    return nullptr;
  const ComputedStyle* parentStyle = parentComputedStyle();
  DCHECK(parentStyle);
  const ComputedStyle* style = computedStyle();
  if (!style || style->animations() || style->transitions())
    return nullptr;
  RefPtr<ComputedStyle> newStyle = ComputedStyle::clone(*style);
  newStyle->propagateIndependentInheritedProperties(*parentStyle);
  INCREMENT_STYLE_STATS_COUNTER(document().styleEngine(),
                                independentInheritedStylesPropagated, 1);
  return newStyle;
}

StyleRecalcChange Element::recalcOwnStyle(StyleRecalcChange change) {
  DCHECK(document().inStyleRecalc());
  DCHECK(!parentOrShadowHostNode()->needsStyleRecalc());
  DCHECK(change >= IndependentInherit || needsStyleRecalc());
  DCHECK(parentComputedStyle());

  RefPtr<ComputedStyle> oldStyle = mutableComputedStyle();

  // When propagating inherited changes, we don't need to do a full style recalc
  // if the only changed properties are independent. In this case, we can simply
  // set these directly on the ComputedStyle object.
  RefPtr<ComputedStyle> newStyle = propagateInheritedProperties(change);
  if (!newStyle)
    newStyle = styleForLayoutObject();
  DCHECK(newStyle);

  StyleRecalcChange localChange =
      ComputedStyle::stylePropagationDiff(oldStyle.get(), newStyle.get());
  if (localChange == NoChange) {
    INCREMENT_STYLE_STATS_COUNTER(document().styleEngine(), stylesUnchanged, 1);
  } else {
    INCREMENT_STYLE_STATS_COUNTER(document().styleEngine(), stylesChanged, 1);
  }

  if (localChange == Reattach) {
    // TODO(nainar): Remove the style parameter being passed into
    // buildLayoutTree().  ComputedStyle will now be stored on Node and accessed
    // in buildLayoutTree() using mutableComputedStyle().
    return buildLayoutTree(*newStyle);
  }

  DCHECK(oldStyle);

  if (localChange != NoChange)
    updateCallbackSelectors(oldStyle.get(), newStyle.get());

  if (LayoutObject* layoutObject = this->layoutObject()) {
    if (localChange != NoChange ||
        pseudoStyleCacheIsInvalid(oldStyle.get(), newStyle.get()) ||
        svgFilterNeedsLayerUpdate()) {
      layoutObject->setStyle(newStyle.get());
    } else {
      // Although no change occurred, we use the new style so that the cousin
      // style sharing code won't get fooled into believing this style is the
      // same.
      // FIXME: We may be able to remove this hack, see discussion in
      // https://codereview.chromium.org/30453002/
      layoutObject->setStyleInternal(newStyle.get());
    }
  }

  if (getStyleChangeType() >= SubtreeStyleChange)
    return Force;

  if (change > Inherit || localChange > Inherit)
    return max(localChange, change);

  if (localChange < IndependentInherit) {
    if (oldStyle->hasChildDependentFlags()) {
      if (childNeedsStyleRecalc())
        return Inherit;
      newStyle->copyChildDependentFlagsFrom(*oldStyle);
    }
    if (oldStyle->hasPseudoElementStyle() || newStyle->hasPseudoElementStyle())
      return UpdatePseudoElements;
  }

  return localChange;
}

StyleRecalcChange Element::buildLayoutTree(ComputedStyle& newStyle) {
  AttachContext reattachContext;
  reattachContext.resolvedStyle = &newStyle;
  bool layoutObjectWillChange = needsAttach() || layoutObject();
  reattachLayoutTree(reattachContext);
  if (layoutObjectWillChange || layoutObject())
    return Reattach;
  return ReattachNoLayoutObject;
}

void Element::updateCallbackSelectors(const ComputedStyle* oldStyle,
                                      const ComputedStyle* newStyle) {
  Vector<String> emptyVector;
  const Vector<String>& oldCallbackSelectors =
      oldStyle ? oldStyle->callbackSelectors() : emptyVector;
  const Vector<String>& newCallbackSelectors =
      newStyle ? newStyle->callbackSelectors() : emptyVector;
  if (oldCallbackSelectors.isEmpty() && newCallbackSelectors.isEmpty())
    return;
  if (oldCallbackSelectors != newCallbackSelectors)
    CSSSelectorWatch::from(document())
        .updateSelectorMatches(oldCallbackSelectors, newCallbackSelectors);
}

void Element::addCallbackSelectors() {
  updateCallbackSelectors(0, computedStyle());
}

void Element::removeCallbackSelectors() {
  updateCallbackSelectors(computedStyle(), 0);
}

ElementShadow* Element::shadow() const {
  return hasRareData() ? elementRareData()->shadow() : nullptr;
}

ElementShadow& Element::ensureShadow() {
  return ensureElementRareData().ensureShadow();
}

void Element::pseudoStateChanged(CSSSelector::PseudoType pseudo) {
  // We can't schedule invaliation sets from inside style recalc otherwise
  // we'd never process them.
  // TODO(esprehn): Make this an ASSERT and fix places that call into this
  // like HTMLSelectElement.
  if (document().inStyleRecalc())
    return;
  document().styleEngine().pseudoStateChangedForElement(pseudo, *this);
}

void Element::setAnimationStyleChange(bool animationStyleChange) {
  if (animationStyleChange && document().inStyleRecalc())
    return;
  if (!hasRareData())
    return;
  if (ElementAnimations* elementAnimations =
          elementRareData()->elementAnimations())
    elementAnimations->setAnimationStyleChange(animationStyleChange);
}

void Element::clearAnimationStyleChange() {
  if (!hasRareData())
    return;
  if (ElementAnimations* elementAnimations =
          elementRareData()->elementAnimations())
    elementAnimations->setAnimationStyleChange(false);
}

void Element::setNeedsAnimationStyleRecalc() {
  if (getStyleChangeType() != NoStyleChange)
    return;

  setNeedsStyleRecalc(LocalStyleChange, StyleChangeReasonForTracing::create(
                                            StyleChangeReason::Animation));
  setAnimationStyleChange(true);
}

void Element::setNeedsCompositingUpdate() {
  if (!document().isActive())
    return;
  LayoutBoxModelObject* layoutObject = layoutBoxModelObject();
  if (!layoutObject)
    return;
  if (!layoutObject->hasLayer())
    return;
  layoutObject->layer()->setNeedsCompositingInputsUpdate();
  // Changes in the return value of requiresAcceleratedCompositing change if
  // the PaintLayer is self-painting.
  layoutObject->layer()->updateSelfPaintingLayer();
}

void Element::v0SetCustomElementDefinition(
    V0CustomElementDefinition* definition) {
  if (!hasRareData() && !definition)
    return;
  DCHECK(!v0CustomElementDefinition());
  ensureElementRareData().v0SetCustomElementDefinition(definition);
}

V0CustomElementDefinition* Element::v0CustomElementDefinition() const {
  if (hasRareData())
    return elementRareData()->v0CustomElementDefinition();
  return nullptr;
}

void Element::setCustomElementDefinition(CustomElementDefinition* definition) {
  DCHECK(definition);
  DCHECK(!customElementDefinition());
  ensureElementRareData().setCustomElementDefinition(definition);
  this->setCustomElementState(CustomElementState::Custom);
}

CustomElementDefinition* Element::customElementDefinition() const {
  if (hasRareData())
    return elementRareData()->customElementDefinition();
  return nullptr;
}

ShadowRoot* Element::createShadowRoot(const ScriptState* scriptState,
                                      ExceptionState& exceptionState) {
  HostsUsingFeatures::countMainWorldOnly(
      scriptState, document(),
      HostsUsingFeatures::Feature::ElementCreateShadowRoot);
  if (ShadowRoot* root = shadowRoot()) {
    if (root->isV1()) {
      exceptionState.throwDOMException(InvalidStateError,
                                       "Shadow root cannot be created on a "
                                       "host which already hosts a v1 shadow "
                                       "tree.");
      return nullptr;
    }
    if (root->type() == ShadowRootType::UserAgent) {
      exceptionState.throwDOMException(InvalidStateError,
                                       "Shadow root cannot be created on a "
                                       "host which already hosts an user-agent "
                                       "shadow tree.");
      return nullptr;
    }
  } else if (alwaysCreateUserAgentShadowRoot()) {
    exceptionState.throwDOMException(InvalidStateError,
                                     "Shadow root cannot be created on a host "
                                     "which already hosts an user-agent shadow "
                                     "tree.");
    return nullptr;
  }
  document().setShadowCascadeOrder(ShadowCascadeOrder::ShadowCascadeV0);

  return createShadowRootInternal(ShadowRootType::V0, exceptionState);
}

ShadowRoot* Element::attachShadow(const ScriptState* scriptState,
                                  const ShadowRootInit& shadowRootInitDict,
                                  ExceptionState& exceptionState) {
  DCHECK(RuntimeEnabledFeatures::shadowDOMV1Enabled());

  HostsUsingFeatures::countMainWorldOnly(
      scriptState, document(),
      HostsUsingFeatures::Feature::ElementAttachShadow);

  const AtomicString& tagName = localName();
  bool tagNameIsSupported =
      isV0CustomElement() ||
      getCustomElementState() != CustomElementState::Uncustomized ||
      tagName == HTMLNames::articleTag || tagName == HTMLNames::asideTag ||
      tagName == HTMLNames::blockquoteTag || tagName == HTMLNames::bodyTag ||
      tagName == HTMLNames::divTag || tagName == HTMLNames::footerTag ||
      tagName == HTMLNames::h1Tag || tagName == HTMLNames::h2Tag ||
      tagName == HTMLNames::h3Tag || tagName == HTMLNames::h4Tag ||
      tagName == HTMLNames::h5Tag || tagName == HTMLNames::h6Tag ||
      tagName == HTMLNames::headerTag || tagName == HTMLNames::navTag ||
      tagName == HTMLNames::pTag || tagName == HTMLNames::sectionTag ||
      tagName == HTMLNames::spanTag;
  if (!tagNameIsSupported) {
    exceptionState.throwDOMException(
        NotSupportedError, "This element does not support attachShadow");
    return nullptr;
  }

  if (shadowRootInitDict.hasMode() && shadowRoot()) {
    exceptionState.throwDOMException(InvalidStateError,
                                     "Shadow root cannot be created on a host "
                                     "which already hosts a shadow tree.");
    return nullptr;
  }

  document().setShadowCascadeOrder(ShadowCascadeOrder::ShadowCascadeV1);

  ShadowRootType type = ShadowRootType::V0;
  if (shadowRootInitDict.hasMode())
    type = shadowRootInitDict.mode() == "open" ? ShadowRootType::Open
                                               : ShadowRootType::Closed;

  if (type == ShadowRootType::Closed)
    UseCounter::count(document(), UseCounter::ElementAttachShadowClosed);
  else if (type == ShadowRootType::Open)
    UseCounter::count(document(), UseCounter::ElementAttachShadowOpen);

  ShadowRoot* shadowRoot = createShadowRootInternal(type, exceptionState);

  if (shadowRootInitDict.hasDelegatesFocus()) {
    shadowRoot->setDelegatesFocus(shadowRootInitDict.delegatesFocus());
    UseCounter::count(document(), UseCounter::ShadowRootDelegatesFocus);
  }

  return shadowRoot;
}

ShadowRoot* Element::createShadowRootInternal(ShadowRootType type,
                                              ExceptionState& exceptionState) {
  DCHECK(!closedShadowRoot());

  if (alwaysCreateUserAgentShadowRoot())
    ensureUserAgentShadowRoot();

  // Some elements make assumptions about what kind of layoutObjects they allow
  // as children so we can't allow author shadows on them for now.
  if (!areAuthorShadowsAllowed()) {
    exceptionState.throwDOMException(
        HierarchyRequestError,
        "Author-created shadow roots are disabled for this element.");
    return nullptr;
  }

  return &ensureShadow().addShadowRoot(*this, type);
}

ShadowRoot* Element::shadowRoot() const {
  ElementShadow* elementShadow = shadow();
  if (!elementShadow)
    return nullptr;
  return &elementShadow->youngestShadowRoot();
}

ShadowRoot* Element::openShadowRoot() const {
  ShadowRoot* root = shadowRoot();
  if (!root)
    return nullptr;
  return root->type() == ShadowRootType::V0 ||
                 root->type() == ShadowRootType::Open
             ? root
             : nullptr;
}

ShadowRoot* Element::closedShadowRoot() const {
  ShadowRoot* root = shadowRoot();
  if (!root)
    return nullptr;
  return root->type() == ShadowRootType::Closed ? root : nullptr;
}

ShadowRoot* Element::authorShadowRoot() const {
  ShadowRoot* root = shadowRoot();
  if (!root)
    return nullptr;
  return root->type() != ShadowRootType::UserAgent ? root : nullptr;
}

ShadowRoot* Element::userAgentShadowRoot() const {
  if (ElementShadow* elementShadow = shadow()) {
    ShadowRoot& root = elementShadow->oldestShadowRoot();
    DCHECK(root.type() == ShadowRootType::UserAgent);
    return &root;
  }

  return nullptr;
}

ShadowRoot& Element::ensureUserAgentShadowRoot() {
  if (ShadowRoot* shadowRoot = userAgentShadowRoot())
    return *shadowRoot;
  ShadowRoot& shadowRoot =
      ensureShadow().addShadowRoot(*this, ShadowRootType::UserAgent);
  didAddUserAgentShadowRoot(shadowRoot);
  return shadowRoot;
}

bool Element::childTypeAllowed(NodeType type) const {
  switch (type) {
    case kElementNode:
    case kTextNode:
    case kCommentNode:
    case kProcessingInstructionNode:
    case kCdataSectionNode:
      return true;
    default:
      break;
  }
  return false;
}

void Element::checkForEmptyStyleChange() {
  const ComputedStyle* style = computedStyle();

  if (!style && !styleAffectedByEmpty())
    return;
  if (!inActiveDocument())
    return;
  if (!document().styleResolver())
    return;

  if (!style ||
      (styleAffectedByEmpty() && (!style->emptyState() || hasChildren())))
    pseudoStateChanged(CSSSelector::PseudoEmpty);
}

void Element::childrenChanged(const ChildrenChange& change) {
  ContainerNode::childrenChanged(change);

  checkForEmptyStyleChange();
  if (!change.byParser && change.isChildElementChange())
    checkForSiblingStyleChanges(
        change.type == ElementRemoved ? SiblingElementRemoved
                                      : SiblingElementInserted,
        toElement(change.siblingChanged), change.siblingBeforeChange,
        change.siblingAfterChange);

  // TODO(hayato): Confirm that we can skip this if a shadow tree is v1.
  if (ElementShadow* shadow = this->shadow())
    shadow->setNeedsDistributionRecalc();
}

void Element::finishParsingChildren() {
  setIsFinishedParsingChildren(true);
  checkForEmptyStyleChange();
  checkForSiblingStyleChanges(FinishedParsingChildren, nullptr, lastChild(),
                              nullptr);
}

AttrNodeList* Element::attrNodeList() {
  return hasRareData() ? elementRareData()->attrNodeList() : nullptr;
}

AttrNodeList& Element::ensureAttrNodeList() {
  return ensureElementRareData().ensureAttrNodeList();
}

void Element::removeAttrNodeList() {
  DCHECK(attrNodeList());
  if (hasRareData())
    elementRareData()->removeAttrNodeList();
}

Attr* Element::setAttributeNode(Attr* attrNode,
                                ExceptionState& exceptionState) {
  Attr* oldAttrNode = attrIfExists(attrNode->getQualifiedName());
  if (oldAttrNode == attrNode)
    return attrNode;  // This Attr is already attached to the element.

  // InUseAttributeError: Raised if node is an Attr that is already an attribute
  // of another Element object.  The DOM user must explicitly clone Attr nodes
  // to re-use them in other elements.
  if (attrNode->ownerElement()) {
    exceptionState.throwDOMException(
        InUseAttributeError,
        "The node provided is an attribute node that is already an attribute "
        "of another Element; attribute nodes must be explicitly cloned.");
    return nullptr;
  }

  if (!isHTMLElement() && attrNode->document().isHTMLDocument() &&
      attrNode->name() != attrNode->name().lower())
    UseCounter::count(
        document(),
        UseCounter::
            NonHTMLElementSetAttributeNodeFromHTMLDocumentNameNotLowercase);

  synchronizeAllAttributes();
  const UniqueElementData& elementData = ensureUniqueElementData();

  AttributeCollection attributes = elementData.attributes();
  size_t index = attributes.findIndex(attrNode->getQualifiedName(),
                                      shouldIgnoreAttributeCase());
  AtomicString localName;
  if (index != kNotFound) {
    const Attribute& attr = attributes[index];

    // If the name of the ElementData attribute doesn't
    // (case-sensitively) match that of the Attr node, record it
    // on the Attr so that it can correctly resolve the value on
    // the Element.
    if (!attr.name().matches(attrNode->getQualifiedName()))
      localName = attr.localName();

    if (oldAttrNode) {
      detachAttrNodeFromElementWithValue(oldAttrNode, attr.value());
    } else {
      // FIXME: using attrNode's name rather than the
      // Attribute's for the replaced Attr is compatible with
      // all but Gecko (and, arguably, the DOM Level1 spec text.)
      // Consider switching.
      oldAttrNode =
          Attr::create(document(), attrNode->getQualifiedName(), attr.value());
    }
  }

  setAttributeInternal(index, attrNode->getQualifiedName(), attrNode->value(),
                       NotInSynchronizationOfLazyAttribute);

  attrNode->attachToElement(this, localName);
  treeScope().adoptIfNeeded(*attrNode);
  ensureAttrNodeList().append(attrNode);

  return oldAttrNode;
}

Attr* Element::setAttributeNodeNS(Attr* attr, ExceptionState& exceptionState) {
  return setAttributeNode(attr, exceptionState);
}

Attr* Element::removeAttributeNode(Attr* attr, ExceptionState& exceptionState) {
  if (attr->ownerElement() != this) {
    exceptionState.throwDOMException(
        NotFoundError, "The node provided is owned by another element.");
    return nullptr;
  }

  DCHECK_EQ(document(), attr->document());

  synchronizeAttribute(attr->getQualifiedName());

  size_t index =
      elementData()->attributes().findIndex(attr->getQualifiedName());
  if (index == kNotFound) {
    exceptionState.throwDOMException(
        NotFoundError, "The attribute was not found on this element.");
    return nullptr;
  }

  detachAttrNodeAtIndex(attr, index);
  return attr;
}

void Element::parseAttribute(const QualifiedName& name,
                             const AtomicString&,
                             const AtomicString& value) {
  if (name == tabindexAttr) {
    int tabindex = 0;
    if (value.isEmpty()) {
      clearTabIndexExplicitlyIfNeeded();
      if (adjustedFocusedElementInTreeScope() == this) {
        // We might want to call blur(), but it's dangerous to dispatch
        // events here.
        document().setNeedsFocusedElementCheck();
      }
    } else if (parseHTMLInteger(value, tabindex)) {
      // Clamp tabindex to the range of 'short' to match Firefox's behavior.
      setTabIndexExplicitly(
          max(static_cast<int>(std::numeric_limits<short>::min()),
              std::min(tabindex,
                       static_cast<int>(std::numeric_limits<short>::max()))));
    }
  } else if (name == XMLNames::langAttr) {
    pseudoStateChanged(CSSSelector::PseudoLang);
  }
}

bool Element::parseAttributeName(QualifiedName& out,
                                 const AtomicString& namespaceURI,
                                 const AtomicString& qualifiedName,
                                 ExceptionState& exceptionState) {
  AtomicString prefix, localName;
  if (!Document::parseQualifiedName(qualifiedName, prefix, localName,
                                    exceptionState))
    return false;
  DCHECK(!exceptionState.hadException());

  QualifiedName qName(prefix, localName, namespaceURI);

  if (!Document::hasValidNamespaceForAttributes(qName)) {
    exceptionState.throwDOMException(
        NamespaceError,
        "'" + namespaceURI + "' is an invalid namespace for attributes.");
    return false;
  }

  out = qName;
  return true;
}

void Element::setAttributeNS(const AtomicString& namespaceURI,
                             const AtomicString& qualifiedName,
                             const AtomicString& value,
                             ExceptionState& exceptionState) {
  QualifiedName parsedName = anyName;
  if (!parseAttributeName(parsedName, namespaceURI, qualifiedName,
                          exceptionState))
    return;
  setAttribute(parsedName, value);
}

void Element::removeAttributeInternal(
    size_t index,
    SynchronizationOfLazyAttribute inSynchronizationOfLazyAttribute) {
  MutableAttributeCollection attributes =
      ensureUniqueElementData().attributes();
  ASSERT_WITH_SECURITY_IMPLICATION(index < attributes.size());

  QualifiedName name = attributes[index].name();
  AtomicString valueBeingRemoved = attributes[index].value();

  if (!inSynchronizationOfLazyAttribute) {
    if (!valueBeingRemoved.isNull())
      willModifyAttribute(name, valueBeingRemoved, nullAtom);
  }

  if (Attr* attrNode = attrIfExists(name))
    detachAttrNodeFromElementWithValue(attrNode, attributes[index].value());

  attributes.remove(index);

  if (!inSynchronizationOfLazyAttribute)
    didRemoveAttribute(name, valueBeingRemoved);
}

void Element::appendAttributeInternal(
    const QualifiedName& name,
    const AtomicString& value,
    SynchronizationOfLazyAttribute inSynchronizationOfLazyAttribute) {
  if (!inSynchronizationOfLazyAttribute)
    willModifyAttribute(name, nullAtom, value);
  ensureUniqueElementData().attributes().append(name, value);
  if (!inSynchronizationOfLazyAttribute)
    didAddAttribute(name, value);
}

void Element::removeAttribute(const AtomicString& name) {
  if (!elementData())
    return;

  AtomicString localName = shouldIgnoreAttributeCase() ? name.lower() : name;
  size_t index = elementData()->attributes().findIndex(localName, false);
  if (index == kNotFound) {
    if (UNLIKELY(localName == styleAttr) &&
        elementData()->m_styleAttributeIsDirty && isStyledElement())
      removeAllInlineStyleProperties();
    return;
  }

  removeAttributeInternal(index, NotInSynchronizationOfLazyAttribute);
}

void Element::removeAttributeNS(const AtomicString& namespaceURI,
                                const AtomicString& localName) {
  removeAttribute(QualifiedName(nullAtom, localName, namespaceURI));
}

Attr* Element::getAttributeNode(const AtomicString& localName) {
  if (!elementData())
    return nullptr;
  synchronizeAttribute(localName);
  const Attribute* attribute =
      elementData()->attributes().find(localName, shouldIgnoreAttributeCase());
  if (!attribute)
    return nullptr;
  return ensureAttr(attribute->name());
}

Attr* Element::getAttributeNodeNS(const AtomicString& namespaceURI,
                                  const AtomicString& localName) {
  if (!elementData())
    return nullptr;
  QualifiedName qName(nullAtom, localName, namespaceURI);
  synchronizeAttribute(qName);
  const Attribute* attribute = elementData()->attributes().find(qName);
  if (!attribute)
    return nullptr;
  return ensureAttr(attribute->name());
}

bool Element::hasAttribute(const AtomicString& localName) const {
  if (!elementData())
    return false;
  synchronizeAttribute(localName);
  return elementData()->attributes().findIndex(
             shouldIgnoreAttributeCase() ? localName.lower() : localName,
             false) != kNotFound;
}

bool Element::hasAttributeNS(const AtomicString& namespaceURI,
                             const AtomicString& localName) const {
  if (!elementData())
    return false;
  QualifiedName qName(nullAtom, localName, namespaceURI);
  synchronizeAttribute(qName);
  return elementData()->attributes().find(qName);
}

void Element::focus(const FocusParams& params) {
  if (!isConnected())
    return;

  if (document().focusedElement() == this)
    return;

  if (!document().isActive())
    return;

  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);
  if (!isFocusable())
    return;

  if (authorShadowRoot() && authorShadowRoot()->delegatesFocus()) {
    if (isShadowIncludingInclusiveAncestorOf(document().focusedElement()))
      return;

    // Slide the focus to its inner node.
    Element* found =
        document().page()->focusController().findFocusableElementInShadowHost(
            *this);
    if (found && isShadowIncludingInclusiveAncestorOf(found)) {
      found->focus(FocusParams(SelectionBehaviorOnFocus::Reset,
                               WebFocusTypeForward, nullptr));
      return;
    }
  }

  if (!document().page()->focusController().setFocusedElement(
          this, document().frame(), params))
    return;

  if (document().focusedElement() == this &&
      UserGestureIndicator::processedUserGestureSinceLoad()) {
    // Bring up the keyboard in the context of anything triggered by a user
    // gesture. Since tracking that across arbitrary boundaries (eg.
    // animations) is difficult, for now we match IE's heuristic and bring
    // up the keyboard if there's been any gesture since load.
    document().page()->chromeClient().showImeIfNeeded();
  }
}

void Element::updateFocusAppearance(
    SelectionBehaviorOnFocus selectionBehavior) {
  if (selectionBehavior == SelectionBehaviorOnFocus::None)
    return;
  if (isRootEditableElement(*this)) {
    LocalFrame* frame = document().frame();
    if (!frame)
      return;

    // When focusing an editable element in an iframe, don't reset the selection
    // if it already contains a selection.
    if (this == frame->selection().rootEditableElement())
      return;

    // FIXME: We should restore the previous selection if there is one.
    VisibleSelection newSelection = createVisibleSelectionDeprecated(
        firstPositionInOrBeforeNode(this), TextAffinity::Downstream);
    // Passing DoNotSetFocus as this function is called after
    // FocusController::setFocusedElement() and we don't want to change the
    // focus to a new Element.
    frame->selection().setSelection(newSelection,
                                    FrameSelection::CloseTyping |
                                        FrameSelection::ClearTypingStyle |
                                        FrameSelection::DoNotSetFocus);

    // TODO(xiaochengh): The use of updateStyleAndLayoutIgnorePendingStylesheets
    // needs to be audited.  See http://crbug.com/590369 for more details.
    document().updateStyleAndLayoutIgnorePendingStylesheets();

    frame->selection().revealSelection();
  } else if (layoutObject() && !layoutObject()->isLayoutPart()) {
    layoutObject()->scrollRectToVisible(boundingBox());
  }
}

void Element::blur() {
  cancelFocusAppearanceUpdate();
  if (adjustedFocusedElementInTreeScope() == this) {
    Document& doc = document();
    if (doc.page())
      doc.page()->focusController().setFocusedElement(0, doc.frame());
    else
      doc.clearFocusedElement();
  }
}

bool Element::supportsFocus() const {
  // FIXME: supportsFocus() can be called when layout is not up to date.
  // Logic that deals with the layoutObject should be moved to
  // layoutObjectIsFocusable().
  // But supportsFocus must return true when the element is editable, or else
  // it won't be focusable. Furthermore, supportsFocus cannot just return true
  // always or else tabIndex() will change for all HTML elements.
  return hasElementFlag(TabIndexWasSetExplicitly) ||
         isRootEditableElement(*this) ||
         (isShadowHost(this) && authorShadowRoot() &&
          authorShadowRoot()->delegatesFocus()) ||
         supportsSpatialNavigationFocus();
}

bool Element::supportsSpatialNavigationFocus() const {
  // This function checks whether the element satisfies the extended criteria
  // for the element to be focusable, introduced by spatial navigation feature,
  // i.e. checks if click or keyboard event handler is specified.
  // This is the way to make it possible to navigate to (focus) elements
  // which web designer meant for being active (made them respond to click
  // events).
  if (!isSpatialNavigationEnabled(document().frame()) ||
      spatialNavigationIgnoresEventHandlers(document().frame()))
    return false;
  if (hasEventListeners(EventTypeNames::click) ||
      hasEventListeners(EventTypeNames::keydown) ||
      hasEventListeners(EventTypeNames::keypress) ||
      hasEventListeners(EventTypeNames::keyup))
    return true;
  if (!isSVGElement())
    return false;
  return (hasEventListeners(EventTypeNames::focus) ||
          hasEventListeners(EventTypeNames::blur) ||
          hasEventListeners(EventTypeNames::focusin) ||
          hasEventListeners(EventTypeNames::focusout));
}

bool Element::isFocusable() const {
  // Style cannot be cleared out for non-active documents, so in that case the
  // needsLayoutTreeUpdateForNode check is invalid.
  DCHECK(!document().isActive() ||
         !document().needsLayoutTreeUpdateForNode(*this));
  return isConnected() && supportsFocus() && !isInert() &&
         layoutObjectIsFocusable();
}

bool Element::isKeyboardFocusable() const {
  return isFocusable() && tabIndex() >= 0;
}

bool Element::isMouseFocusable() const {
  return isFocusable();
}

bool Element::isFocusedElementInDocument() const {
  return this == document().focusedElement();
}

Element* Element::adjustedFocusedElementInTreeScope() const {
  return isInTreeScope() ? containingTreeScope().adjustedFocusedElement()
                         : nullptr;
}

void Element::dispatchFocusEvent(Element* oldFocusedElement,
                                 WebFocusType type,
                                 InputDeviceCapabilities* sourceCapabilities) {
  dispatchEvent(FocusEvent::create(EventTypeNames::focus, false, false,
                                   document().domWindow(), 0, oldFocusedElement,
                                   sourceCapabilities));
}

void Element::dispatchBlurEvent(Element* newFocusedElement,
                                WebFocusType type,
                                InputDeviceCapabilities* sourceCapabilities) {
  dispatchEvent(FocusEvent::create(EventTypeNames::blur, false, false,
                                   document().domWindow(), 0, newFocusedElement,
                                   sourceCapabilities));
}

void Element::dispatchFocusInEvent(
    const AtomicString& eventType,
    Element* oldFocusedElement,
    WebFocusType,
    InputDeviceCapabilities* sourceCapabilities) {
#if DCHECK_IS_ON()
  DCHECK(!EventDispatchForbiddenScope::isEventDispatchForbidden());
#endif
  DCHECK(eventType == EventTypeNames::focusin ||
         eventType == EventTypeNames::DOMFocusIn);
  dispatchScopedEvent(
      FocusEvent::create(eventType, true, false, document().domWindow(), 0,
                         oldFocusedElement, sourceCapabilities));
}

void Element::dispatchFocusOutEvent(
    const AtomicString& eventType,
    Element* newFocusedElement,
    InputDeviceCapabilities* sourceCapabilities) {
#if DCHECK_IS_ON()
  DCHECK(!EventDispatchForbiddenScope::isEventDispatchForbidden());
#endif
  DCHECK(eventType == EventTypeNames::focusout ||
         eventType == EventTypeNames::DOMFocusOut);
  dispatchScopedEvent(
      FocusEvent::create(eventType, true, false, document().domWindow(), 0,
                         newFocusedElement, sourceCapabilities));
}

String Element::innerHTML() const {
  return createMarkup(this, ChildrenOnly);
}

String Element::outerHTML() const {
  return createMarkup(this);
}

void Element::setInnerHTML(const String& html, ExceptionState& exceptionState) {
  InspectorInstrumentation::NativeBreakpoint nativeBreakpoint(
      &document(), "setInnerHTML", true);
  if (DocumentFragment* fragment = createFragmentForInnerOuterHTML(
          html, this, AllowScriptingContent, "innerHTML", exceptionState)) {
    ContainerNode* container = this;
    if (isHTMLTemplateElement(*this))
      container = toHTMLTemplateElement(this)->content();
    replaceChildrenWithFragment(container, fragment, exceptionState);
  }
}

void Element::setOuterHTML(const String& html, ExceptionState& exceptionState) {
  Node* p = parentNode();
  if (!p) {
    exceptionState.throwDOMException(NoModificationAllowedError,
                                     "This element has no parent node.");
    return;
  }
  if (!p->isElementNode()) {
    exceptionState.throwDOMException(NoModificationAllowedError,
                                     "This element's parent is of type '" +
                                         p->nodeName() +
                                         "', which is not an element node.");
    return;
  }

  Element* parent = toElement(p);
  Node* prev = previousSibling();
  Node* next = nextSibling();

  DocumentFragment* fragment = createFragmentForInnerOuterHTML(
      html, parent, AllowScriptingContent, "outerHTML", exceptionState);
  if (exceptionState.hadException())
    return;

  parent->replaceChild(fragment, this, exceptionState);
  Node* node = next ? next->previousSibling() : nullptr;
  if (!exceptionState.hadException() && node && node->isTextNode())
    mergeWithNextTextNode(toText(node), exceptionState);

  if (!exceptionState.hadException() && prev && prev->isTextNode())
    mergeWithNextTextNode(toText(prev), exceptionState);
}

Node* Element::insertAdjacent(const String& where,
                              Node* newChild,
                              ExceptionState& exceptionState) {
  if (equalIgnoringCase(where, "beforeBegin")) {
    if (ContainerNode* parent = this->parentNode()) {
      parent->insertBefore(newChild, this, exceptionState);
      if (!exceptionState.hadException())
        return newChild;
    }
    return nullptr;
  }

  if (equalIgnoringCase(where, "afterBegin")) {
    insertBefore(newChild, firstChild(), exceptionState);
    return exceptionState.hadException() ? nullptr : newChild;
  }

  if (equalIgnoringCase(where, "beforeEnd")) {
    appendChild(newChild, exceptionState);
    return exceptionState.hadException() ? nullptr : newChild;
  }

  if (equalIgnoringCase(where, "afterEnd")) {
    if (ContainerNode* parent = this->parentNode()) {
      parent->insertBefore(newChild, nextSibling(), exceptionState);
      if (!exceptionState.hadException())
        return newChild;
    }
    return nullptr;
  }

  exceptionState.throwDOMException(
      SyntaxError, "The value provided ('" + where +
                       "') is not one of 'beforeBegin', 'afterBegin', "
                       "'beforeEnd', or 'afterEnd'.");
  return nullptr;
}

NodeIntersectionObserverData* Element::intersectionObserverData() const {
  if (hasRareData())
    return elementRareData()->intersectionObserverData();
  return nullptr;
}

NodeIntersectionObserverData& Element::ensureIntersectionObserverData() {
  return ensureElementRareData().ensureIntersectionObserverData();
}

HeapHashMap<Member<ResizeObserver>, Member<ResizeObservation>>*
Element::resizeObserverData() const {
  if (hasRareData())
    return elementRareData()->resizeObserverData();
  return nullptr;
}

HeapHashMap<Member<ResizeObserver>, Member<ResizeObservation>>&
Element::ensureResizeObserverData() {
  return ensureElementRareData().ensureResizeObserverData();
}

void Element::setNeedsResizeObserverUpdate() {
  if (auto* data = resizeObserverData()) {
    for (auto& observation : data->values())
      observation->elementSizeChanged();
  }
}

// Step 1 of http://domparsing.spec.whatwg.org/#insertadjacenthtml()
static Element* contextElementForInsertion(const String& where,
                                           Element* element,
                                           ExceptionState& exceptionState) {
  if (equalIgnoringCase(where, "beforeBegin") ||
      equalIgnoringCase(where, "afterEnd")) {
    Element* parent = element->parentElement();
    if (!parent) {
      exceptionState.throwDOMException(NoModificationAllowedError,
                                       "The element has no parent.");
      return nullptr;
    }
    return parent;
  }
  if (equalIgnoringCase(where, "afterBegin") ||
      equalIgnoringCase(where, "beforeEnd"))
    return element;
  exceptionState.throwDOMException(
      SyntaxError, "The value provided ('" + where +
                       "') is not one of 'beforeBegin', 'afterBegin', "
                       "'beforeEnd', or 'afterEnd'.");
  return nullptr;
}

Element* Element::insertAdjacentElement(const String& where,
                                        Element* newChild,
                                        ExceptionState& exceptionState) {
  Node* returnValue = insertAdjacent(where, newChild, exceptionState);
  return toElement(returnValue);
}

void Element::insertAdjacentText(const String& where,
                                 const String& text,
                                 ExceptionState& exceptionState) {
  insertAdjacent(where, document().createTextNode(text), exceptionState);
}

void Element::insertAdjacentHTML(const String& where,
                                 const String& markup,
                                 ExceptionState& exceptionState) {
  Element* contextElement =
      contextElementForInsertion(where, this, exceptionState);
  if (!contextElement)
    return;

  DocumentFragment* fragment = createFragmentForInnerOuterHTML(
      markup, contextElement, AllowScriptingContent, "insertAdjacentHTML",
      exceptionState);
  if (!fragment)
    return;
  insertAdjacent(where, fragment, exceptionState);
}

void Element::setPointerCapture(int pointerId, ExceptionState& exceptionState) {
  if (document().frame()) {
    if (!document().frame()->eventHandler().isPointerEventActive(pointerId))
      exceptionState.throwDOMException(InvalidPointerId, "InvalidPointerId");
    else if (!isConnected())
      exceptionState.throwDOMException(InvalidStateError, "InvalidStateError");
    else
      document().frame()->eventHandler().setPointerCapture(pointerId, this);
  }
}

void Element::releasePointerCapture(int pointerId,
                                    ExceptionState& exceptionState) {
  if (document().frame()) {
    if (!document().frame()->eventHandler().isPointerEventActive(pointerId))
      exceptionState.throwDOMException(InvalidPointerId, "InvalidPointerId");
    else
      document().frame()->eventHandler().releasePointerCapture(pointerId, this);
  }
}

bool Element::hasPointerCapture(int pointerId) const {
  return document().frame() &&
         document().frame()->eventHandler().hasPointerCapture(pointerId, this);
}

bool Element::hasProcessedPointerCapture(int pointerId) const {
  return document().frame() &&
         document().frame()->eventHandler().hasProcessedPointerCapture(
             pointerId, this);
}

String Element::innerText() {
  // We need to update layout, since plainText uses line boxes in the layout
  // tree.
  document().updateStyleAndLayoutIgnorePendingStylesheetsForNode(this);

  if (!layoutObject())
    return textContent(true);

  return plainText(EphemeralRange::rangeOfContents(*this),
                   TextIteratorForInnerText);
}

String Element::outerText() {
  // Getting outerText is the same as getting innerText, only
  // setting is different. You would think this should get the plain
  // text for the outer range, but this is wrong, <br> for instance
  // would return different values for inner and outer text by such
  // a rule, but it doesn't in WinIE, and we want to match that.
  return innerText();
}

String Element::textFromChildren() {
  Text* firstTextNode = 0;
  bool foundMultipleTextNodes = false;
  unsigned totalLength = 0;

  for (Node* child = firstChild(); child; child = child->nextSibling()) {
    if (!child->isTextNode())
      continue;
    Text* text = toText(child);
    if (!firstTextNode)
      firstTextNode = text;
    else
      foundMultipleTextNodes = true;
    unsigned length = text->data().length();
    if (length > std::numeric_limits<unsigned>::max() - totalLength)
      return emptyString();
    totalLength += length;
  }

  if (!firstTextNode)
    return emptyString();

  if (firstTextNode && !foundMultipleTextNodes) {
    firstTextNode->atomize();
    return firstTextNode->data();
  }

  StringBuilder content;
  content.reserveCapacity(totalLength);
  for (Node* child = firstTextNode; child; child = child->nextSibling()) {
    if (!child->isTextNode())
      continue;
    content.append(toText(child)->data());
  }

  DCHECK_EQ(content.length(), totalLength);
  return content.toString();
}

const AtomicString& Element::shadowPseudoId() const {
  if (ShadowRoot* root = containingShadowRoot()) {
    if (root->type() == ShadowRootType::UserAgent)
      return fastGetAttribute(pseudoAttr);
  }
  return nullAtom;
}

void Element::setShadowPseudoId(const AtomicString& id) {
  DCHECK(CSSSelector::parsePseudoType(id, false) ==
             CSSSelector::PseudoWebKitCustomElement ||
         CSSSelector::parsePseudoType(id, false) ==
             CSSSelector::PseudoBlinkInternalElement);
  setAttribute(pseudoAttr, id);
}

bool Element::isInDescendantTreeOf(const Element* shadowHost) const {
  DCHECK(shadowHost);
  DCHECK(isShadowHost(shadowHost));

  for (const Element* ancestorShadowHost = this->ownerShadowHost();
       ancestorShadowHost;
       ancestorShadowHost = ancestorShadowHost->ownerShadowHost()) {
    if (ancestorShadowHost == shadowHost)
      return true;
  }
  return false;
}

LayoutSize Element::minimumSizeForResizing() const {
  return hasRareData() ? elementRareData()->minimumSizeForResizing()
                       : defaultMinimumSizeForResizing();
}

void Element::setMinimumSizeForResizing(const LayoutSize& size) {
  if (!hasRareData() && size == defaultMinimumSizeForResizing())
    return;
  ensureElementRareData().setMinimumSizeForResizing(size);
}

const ComputedStyle* Element::ensureComputedStyle(
    PseudoId pseudoElementSpecifier) {
  if (PseudoElement* element = pseudoElement(pseudoElementSpecifier))
    return element->ensureComputedStyle();

  if (!inActiveDocument()) {
    // FIXME: Try to do better than this. Ensure that styleForElement() works
    // for elements that are not in the document tree and figure out when to
    // destroy the computed style for such elements.
    return nullptr;
  }

  // FIXME: Find and use the layoutObject from the pseudo element instead of the
  // actual element so that the 'length' properties, which are only known by the
  // layoutObject because it did the layout, will be correct and so that the
  // values returned for the ":selection" pseudo-element will be correct.
  ComputedStyle* elementStyle = mutableComputedStyle();
  if (!elementStyle) {
    ElementRareData& rareData = ensureElementRareData();
    if (!rareData.computedStyle())
      rareData.setComputedStyle(
          document().styleForElementIgnoringPendingStylesheets(this));
    elementStyle = rareData.computedStyle();
  }

  if (!pseudoElementSpecifier)
    return elementStyle;

  if (ComputedStyle* pseudoElementStyle =
          elementStyle->getCachedPseudoStyle(pseudoElementSpecifier))
    return pseudoElementStyle;

  RefPtr<ComputedStyle> result =
      document().ensureStyleResolver().pseudoStyleForElement(
          this, PseudoStyleRequest(pseudoElementSpecifier,
                                   PseudoStyleRequest::ForComputedStyle),
          elementStyle);
  DCHECK(result);
  return elementStyle->addCachedPseudoStyle(result.release());
}

AtomicString Element::computeInheritedLanguage() const {
  const Node* n = this;
  AtomicString value;
  // The language property is inherited, so we iterate over the parents to find
  // the first language.
  do {
    if (n->isElementNode()) {
      if (const ElementData* elementData = toElement(n)->elementData()) {
        AttributeCollection attributes = elementData->attributes();
        // Spec: xml:lang takes precedence -- http://www.w3.org/TR/xhtml1/#C_7
        if (const Attribute* attribute = attributes.find(XMLNames::langAttr))
          value = attribute->value();
        else if (const Attribute* attribute =
                     attributes.find(HTMLNames::langAttr))
          value = attribute->value();
      }
    } else if (n->isDocumentNode()) {
      // checking the MIME content-language
      value = toDocument(n)->contentLanguage();
    }

    n = n->parentOrShadowHostNode();
  } while (n && value.isNull());

  return value;
}

Locale& Element::locale() const {
  return document().getCachedLocale(computeInheritedLanguage());
}

void Element::cancelFocusAppearanceUpdate() {
  if (document().focusedElement() == this)
    document().cancelFocusAppearanceUpdate();
}

void Element::updatePseudoElement(PseudoId pseudoId, StyleRecalcChange change) {
  DCHECK(!needsStyleRecalc());
  PseudoElement* element = pseudoElement(pseudoId);

  if (element && (change == UpdatePseudoElements ||
                  element->shouldCallRecalcStyle(change))) {
    if (pseudoId == PseudoIdFirstLetter && updateFirstLetter(element))
      return;

    // Need to clear the cached style if the PseudoElement wants a recalc so it
    // computes a new style.
    if (element->needsStyleRecalc())
      layoutObject()->mutableStyle()->removeCachedPseudoStyle(pseudoId);

    // PseudoElement styles hang off their parent element's style so if we
    // needed a style recalc we should Force one on the pseudo.  FIXME: We
    // should figure out the right text sibling to pass.
    element->recalcStyle(change == UpdatePseudoElements ? Force : change);

    // Wait until our parent is not displayed or
    // pseudoElementLayoutObjectIsNeeded is false, otherwise we could
    // continuously create and destroy PseudoElements when
    // LayoutObject::isChildAllowed on our parent returns false for the
    // PseudoElement's layoutObject for each style recalc.
    if (!layoutObject() ||
        !pseudoElementLayoutObjectIsNeeded(
            layoutObject()->getCachedPseudoStyle(pseudoId)))
      elementRareData()->setPseudoElement(pseudoId, nullptr);
  } else if (pseudoId == PseudoIdFirstLetter && element &&
             change >= UpdatePseudoElements &&
             !FirstLetterPseudoElement::firstLetterTextLayoutObject(*element)) {
    // This can happen if we change to a float, for example. We need to cleanup
    // the first-letter pseudoElement and then fix the text of the original
    // remaining text layoutObject.  This can be seen in Test 7 of
    // fast/css/first-letter-removed-added.html
    elementRareData()->setPseudoElement(pseudoId, nullptr);
  } else if (change >= UpdatePseudoElements) {
    createPseudoElementIfNeeded(pseudoId);
  }
}

// If we're updating first letter, and the current first letter layoutObject
// is not the same as the one we're currently using we need to re-create
// the first letter layoutObject.
bool Element::updateFirstLetter(Element* element) {
  LayoutObject* remainingTextLayoutObject =
      FirstLetterPseudoElement::firstLetterTextLayoutObject(*element);
  if (!remainingTextLayoutObject ||
      remainingTextLayoutObject !=
          toFirstLetterPseudoElement(element)->remainingTextLayoutObject()) {
    // We have to clear out the old first letter here because when it is
    // disposed it will set the original text back on the remaining text
    // layoutObject. If we dispose after creating the new one we will get
    // incorrect results due to setting the first letter back.
    if (remainingTextLayoutObject)
      element->reattachLayoutTree();
    else
      elementRareData()->setPseudoElement(PseudoIdFirstLetter, nullptr);
    return true;
  }
  return false;
}

void Element::createPseudoElementIfNeeded(PseudoId pseudoId) {
  if (isPseudoElement())
    return;

  // Document::ensureStyleResolver is not inlined and shows up on profiles,
  // avoid it here.
  PseudoElement* element =
      document().styleEngine().ensureResolver().createPseudoElementIfNeeded(
          *this, pseudoId);
  if (!element)
    return;

  if (pseudoId == PseudoIdBackdrop)
    document().addToTopLayer(element, this);
  element->insertedInto(this);
  element->attachLayoutTree();

  InspectorInstrumentation::pseudoElementCreated(element);

  ensureElementRareData().setPseudoElement(pseudoId, element);
}

PseudoElement* Element::pseudoElement(PseudoId pseudoId) const {
  return hasRareData() ? elementRareData()->pseudoElement(pseudoId) : nullptr;
}

LayoutObject* Element::pseudoElementLayoutObject(PseudoId pseudoId) const {
  if (PseudoElement* element = pseudoElement(pseudoId))
    return element->layoutObject();
  return nullptr;
}

bool Element::matches(const String& selectors, ExceptionState& exceptionState) {
  SelectorQuery* selectorQuery = document().selectorQueryCache().add(
      AtomicString(selectors), document(), exceptionState);
  if (!selectorQuery)
    return false;
  return selectorQuery->matches(*this);
}

Element* Element::closest(const String& selectors,
                          ExceptionState& exceptionState) {
  SelectorQuery* selectorQuery = document().selectorQueryCache().add(
      AtomicString(selectors), document(), exceptionState);
  if (!selectorQuery)
    return nullptr;
  return selectorQuery->closest(*this);
}

DOMTokenList& Element::classList() {
  ElementRareData& rareData = ensureElementRareData();
  if (!rareData.classList())
    rareData.setClassList(ClassList::create(this));
  return *rareData.classList();
}

DOMStringMap& Element::dataset() {
  ElementRareData& rareData = ensureElementRareData();
  if (!rareData.dataset())
    rareData.setDataset(DatasetDOMStringMap::create(this));
  return *rareData.dataset();
}

KURL Element::hrefURL() const {
  // FIXME: These all have href() or url(), but no common super class. Why
  // doesn't <link> implement URLUtils?
  if (isHTMLAnchorElement(*this) || isHTMLAreaElement(*this) ||
      isHTMLLinkElement(*this))
    return getURLAttribute(hrefAttr);
  if (isSVGAElement(*this))
    return toSVGAElement(*this).legacyHrefURL(document());
  return KURL();
}

KURL Element::getURLAttribute(const QualifiedName& name) const {
#if DCHECK_IS_ON()
  if (elementData()) {
    if (const Attribute* attribute = attributes().find(name))
      DCHECK(isURLAttribute(*attribute));
  }
#endif
  return document().completeURL(
      stripLeadingAndTrailingHTMLSpaces(getAttribute(name)));
}

KURL Element::getNonEmptyURLAttribute(const QualifiedName& name) const {
#if DCHECK_IS_ON()
  if (elementData()) {
    if (const Attribute* attribute = attributes().find(name))
      DCHECK(isURLAttribute(*attribute));
  }
#endif
  String value = stripLeadingAndTrailingHTMLSpaces(getAttribute(name));
  if (value.isEmpty())
    return KURL();
  return document().completeURL(value);
}

int Element::getIntegralAttribute(const QualifiedName& attributeName) const {
  return getAttribute(attributeName).toInt();
}

void Element::setIntegralAttribute(const QualifiedName& attributeName,
                                   int value) {
  setAttribute(attributeName, AtomicString::number(value));
}

void Element::setUnsignedIntegralAttribute(const QualifiedName& attributeName,
                                           unsigned value) {
  // Range restrictions are enforced for unsigned IDL attributes that
  // reflect content attributes,
  //   http://www.whatwg.org/specs/web-apps/current-work/multipage/common-dom-interfaces.html#reflecting-content-attributes-in-idl-attributes
  if (value > 0x7fffffffu)
    value = 0;
  setAttribute(attributeName, AtomicString::number(value));
}

double Element::getFloatingPointAttribute(const QualifiedName& attributeName,
                                          double fallbackValue) const {
  return parseToDoubleForNumberType(getAttribute(attributeName), fallbackValue);
}

void Element::setFloatingPointAttribute(const QualifiedName& attributeName,
                                        double value) {
  setAttribute(attributeName, AtomicString::number(value));
}

void Element::setContainsFullScreenElement(bool flag) {
  setElementFlag(ContainsFullScreenElement, flag);
  document().styleEngine().ensureFullscreenUAStyle();
  pseudoStateChanged(CSSSelector::PseudoFullScreenAncestor);
}

// Unlike Node::parentOrShadowHostElement, this can cross frame boundaries.
static Element* nextAncestorElement(Element* element) {
  DCHECK(element);
  if (element->parentOrShadowHostElement())
    return element->parentOrShadowHostElement();

  Frame* frame = element->document().frame();
  if (!frame || !frame->owner())
    return nullptr;

  // Find the next LocalFrame on the ancestor chain, and return the
  // corresponding <iframe> element for the remote child if it exists.
  while (frame->tree().parent() && frame->tree().parent()->isRemoteFrame())
    frame = frame->tree().parent();

  if (frame->owner() && frame->owner()->isLocal())
    return toHTMLFrameOwnerElement(frame->owner());

  return nullptr;
}

void Element::setContainsFullScreenElementOnAncestorsCrossingFrameBoundaries(
    bool flag) {
  for (Element* element = nextAncestorElement(this); element;
       element = nextAncestorElement(element))
    element->setContainsFullScreenElement(flag);
}

void Element::setIsInTopLayer(bool inTopLayer) {
  if (isInTopLayer() == inTopLayer)
    return;
  setElementFlag(IsInTopLayer, inTopLayer);

  // We must ensure a reattach occurs so the layoutObject is inserted in the
  // correct sibling order under LayoutView according to its top layer position,
  // or in its usual place if not in the top layer.
  lazyReattachIfAttached();
}

void Element::requestPointerLock() {
  if (document().page())
    document().page()->pointerLockController().requestPointerLock(this);
}

SpellcheckAttributeState Element::spellcheckAttributeState() const {
  const AtomicString& value = fastGetAttribute(spellcheckAttr);
  if (value == nullAtom)
    return SpellcheckAttributeDefault;
  if (equalIgnoringCase(value, "true") || equalIgnoringCase(value, ""))
    return SpellcheckAttributeTrue;
  if (equalIgnoringCase(value, "false"))
    return SpellcheckAttributeFalse;

  return SpellcheckAttributeDefault;
}

bool Element::isSpellCheckingEnabled() const {
  for (const Element* element = this; element;
       element = element->parentOrShadowHostElement()) {
    switch (element->spellcheckAttributeState()) {
      case SpellcheckAttributeTrue:
        return true;
      case SpellcheckAttributeFalse:
        return false;
      case SpellcheckAttributeDefault:
        break;
    }
  }

  if (!document().page())
    return true;

  return document().page()->settings().spellCheckEnabledByDefault();
}

#if DCHECK_IS_ON()
bool Element::fastAttributeLookupAllowed(const QualifiedName& name) const {
  if (name == HTMLNames::styleAttr)
    return false;

  if (isSVGElement())
    return !toSVGElement(this)->isAnimatableAttribute(name);

  return true;
}
#endif

#ifdef DUMP_NODE_STATISTICS
bool Element::hasNamedNodeMap() const {
  return hasRareData() && elementRareData()->attributeMap();
}
#endif

inline void Element::updateName(const AtomicString& oldName,
                                const AtomicString& newName) {
  if (!isInDocumentTree())
    return;

  if (oldName == newName)
    return;

  if (shouldRegisterAsNamedItem())
    updateNamedItemRegistration(oldName, newName);
}

inline void Element::updateId(const AtomicString& oldId,
                              const AtomicString& newId) {
  if (!isInTreeScope())
    return;

  if (oldId == newId)
    return;

  updateId(containingTreeScope(), oldId, newId);
}

inline void Element::updateId(TreeScope& scope,
                              const AtomicString& oldId,
                              const AtomicString& newId) {
  DCHECK(isInTreeScope());
  DCHECK_NE(oldId, newId);

  if (!oldId.isEmpty())
    scope.removeElementById(oldId, this);
  if (!newId.isEmpty())
    scope.addElementById(newId, this);

  if (shouldRegisterAsExtraNamedItem())
    updateExtraNamedItemRegistration(oldId, newId);
}

void Element::willModifyAttribute(const QualifiedName& name,
                                  const AtomicString& oldValue,
                                  const AtomicString& newValue) {
  if (name == HTMLNames::nameAttr) {
    updateName(oldValue, newValue);
  }

  if (oldValue != newValue) {
    document().styleEngine().attributeChangedForElement(name, *this);
    if (getCustomElementState() == CustomElementState::Custom)
      CustomElement::enqueueAttributeChangedCallback(this, name, oldValue,
                                                     newValue);
    else if (isUpgradedV0CustomElement())
      V0CustomElement::attributeDidChange(this, name.localName(), oldValue,
                                          newValue);
  }

  if (MutationObserverInterestGroup* recipients =
          MutationObserverInterestGroup::createForAttributesMutation(*this,
                                                                     name))
    recipients->enqueueMutationRecord(
        MutationRecord::createAttributes(this, name, oldValue));

  InspectorInstrumentation::willModifyDOMAttr(this, oldValue, newValue);
}

DISABLE_CFI_PERF
void Element::didAddAttribute(const QualifiedName& name,
                              const AtomicString& value) {
  if (name == HTMLNames::idAttr)
    updateId(nullAtom, value);
  attributeChanged(name, nullAtom, value);
  InspectorInstrumentation::didModifyDOMAttr(this, name, value);
  dispatchSubtreeModifiedEvent();
}

void Element::didModifyAttribute(const QualifiedName& name,
                                 const AtomicString& oldValue,
                                 const AtomicString& newValue) {
  if (name == HTMLNames::idAttr)
    updateId(oldValue, newValue);
  attributeChanged(name, oldValue, newValue);
  InspectorInstrumentation::didModifyDOMAttr(this, name, newValue);
  // Do not dispatch a DOMSubtreeModified event here; see bug 81141.
}

void Element::didRemoveAttribute(const QualifiedName& name,
                                 const AtomicString& oldValue) {
  if (name == HTMLNames::idAttr)
    updateId(oldValue, nullAtom);
  attributeChanged(name, oldValue, nullAtom);
  InspectorInstrumentation::didRemoveDOMAttr(this, name);
  dispatchSubtreeModifiedEvent();
}

static bool needsURLResolutionForInlineStyle(const Element& element,
                                             const Document& oldDocument,
                                             const Document& newDocument) {
  if (oldDocument == newDocument)
    return false;
  if (oldDocument.baseURL() == newDocument.baseURL())
    return false;
  const StylePropertySet* style = element.inlineStyle();
  if (!style)
    return false;
  for (unsigned i = 0; i < style->propertyCount(); ++i) {
    // FIXME: Should handle all URL-based properties: CSSImageSetValue,
    // CSSCursorImageValue, etc.
    if (style->propertyAt(i).value().isImageValue())
      return true;
  }
  return false;
}

static void reResolveURLsInInlineStyle(const Document& document,
                                       MutableStylePropertySet& style) {
  for (unsigned i = 0; i < style.propertyCount(); ++i) {
    StylePropertySet::PropertyReference property = style.propertyAt(i);
    // FIXME: Should handle all URL-based properties: CSSImageSetValue,
    // CSSCursorImageValue, etc.
    if (property.value().isImageValue())
      toCSSImageValue(property.value()).reResolveURL(document);
  }
}

void Element::didMoveToNewDocument(Document& oldDocument) {
  Node::didMoveToNewDocument(oldDocument);

  // If the documents differ by quirks mode then they differ by case sensitivity
  // for class and id names so we need to go through the attribute change logic
  // to pick up the new casing in the ElementData.
  if (oldDocument.inQuirksMode() != document().inQuirksMode()) {
    if (hasID())
      setIdAttribute(getIdAttribute());
    if (hasClass())
      setAttribute(HTMLNames::classAttr, getClassAttribute());
  }

  if (needsURLResolutionForInlineStyle(*this, oldDocument, document()))
    reResolveURLsInInlineStyle(document(), ensureMutableInlineStyle());
}

void Element::updateNamedItemRegistration(const AtomicString& oldName,
                                          const AtomicString& newName) {
  if (!document().isHTMLDocument())
    return;

  if (!oldName.isEmpty())
    toHTMLDocument(document()).removeNamedItem(oldName);

  if (!newName.isEmpty())
    toHTMLDocument(document()).addNamedItem(newName);
}

void Element::updateExtraNamedItemRegistration(const AtomicString& oldId,
                                               const AtomicString& newId) {
  if (!document().isHTMLDocument())
    return;

  if (!oldId.isEmpty())
    toHTMLDocument(document()).removeExtraNamedItem(oldId);

  if (!newId.isEmpty())
    toHTMLDocument(document()).addExtraNamedItem(newId);
}

void Element::scheduleSVGFilterLayerUpdateHack() {
  document().scheduleSVGFilterLayerUpdateHack(*this);
}

IntSize Element::savedLayerScrollOffset() const {
  return hasRareData() ? elementRareData()->savedLayerScrollOffset()
                       : IntSize();
}

void Element::setSavedLayerScrollOffset(const IntSize& size) {
  if (size.isZero() && !hasRareData())
    return;
  ensureElementRareData().setSavedLayerScrollOffset(size);
}

Attr* Element::attrIfExists(const QualifiedName& name) {
  if (AttrNodeList* attrNodeList = this->attrNodeList()) {
    bool shouldIgnoreCase = shouldIgnoreAttributeCase();
    for (const auto& attr : *attrNodeList) {
      if (attr->getQualifiedName().matchesPossiblyIgnoringCase(
              name, shouldIgnoreCase))
        return attr.get();
    }
  }
  return nullptr;
}

Attr* Element::ensureAttr(const QualifiedName& name) {
  Attr* attrNode = attrIfExists(name);
  if (!attrNode) {
    attrNode = Attr::create(*this, name);
    treeScope().adoptIfNeeded(*attrNode);
    ensureAttrNodeList().append(attrNode);
  }
  return attrNode;
}

void Element::detachAttrNodeFromElementWithValue(Attr* attrNode,
                                                 const AtomicString& value) {
  DCHECK(attrNodeList());
  attrNode->detachFromElementWithValue(value);

  AttrNodeList* list = attrNodeList();
  size_t index = list->find(attrNode);
  DCHECK_NE(index, kNotFound);
  list->remove(index);
  if (list->isEmpty())
    removeAttrNodeList();
}

void Element::detachAllAttrNodesFromElement() {
  AttrNodeList* list = this->attrNodeList();
  if (!list)
    return;

  AttributeCollection attributes = elementData()->attributes();
  for (const Attribute& attr : attributes) {
    if (Attr* attrNode = attrIfExists(attr.name()))
      attrNode->detachFromElementWithValue(attr.value());
  }

  removeAttrNodeList();
}

void Element::willRecalcStyle(StyleRecalcChange) {
  DCHECK(hasCustomStyleCallbacks());
}

void Element::didRecalcStyle(StyleRecalcChange) {
  DCHECK(hasCustomStyleCallbacks());
}

PassRefPtr<ComputedStyle> Element::customStyleForLayoutObject() {
  DCHECK(hasCustomStyleCallbacks());
  return nullptr;
}

void Element::cloneAttributesFromElement(const Element& other) {
  if (hasRareData())
    detachAllAttrNodesFromElement();

  other.synchronizeAllAttributes();
  if (!other.m_elementData) {
    m_elementData.clear();
    return;
  }

  const AtomicString& oldID = getIdAttribute();
  const AtomicString& newID = other.getIdAttribute();

  if (!oldID.isNull() || !newID.isNull())
    updateId(oldID, newID);

  const AtomicString& oldName = getNameAttribute();
  const AtomicString& newName = other.getNameAttribute();

  if (!oldName.isNull() || !newName.isNull())
    updateName(oldName, newName);

  // Quirks mode makes class and id not case sensitive. We can't share the
  // ElementData if the idForStyleResolution and the className need different
  // casing.
  bool ownerDocumentsHaveDifferentCaseSensitivity = false;
  if (other.hasClass() || other.hasID())
    ownerDocumentsHaveDifferentCaseSensitivity =
        other.document().inQuirksMode() != document().inQuirksMode();

  // If 'other' has a mutable ElementData, convert it to an immutable one so we
  // can share it between both elements.
  // We can only do this if there are no presentation attributes and sharing the
  // data won't result in different case sensitivity of class or id.
  if (other.m_elementData->isUnique() &&
      !ownerDocumentsHaveDifferentCaseSensitivity &&
      !other.m_elementData->presentationAttributeStyle())
    const_cast<Element&>(other).m_elementData =
        toUniqueElementData(other.m_elementData)->makeShareableCopy();

  if (!other.m_elementData->isUnique() &&
      !ownerDocumentsHaveDifferentCaseSensitivity &&
      !needsURLResolutionForInlineStyle(other, other.document(), document()))
    m_elementData = other.m_elementData;
  else
    m_elementData = other.m_elementData->makeUniqueCopy();

  AttributeCollection attributes = m_elementData->attributes();
  for (const Attribute& attr : attributes)
    attributeChangedFromParserOrByCloning(attr.name(), attr.value(),
                                          ModifiedByCloning);
}

void Element::cloneDataFromElement(const Element& other) {
  cloneAttributesFromElement(other);
  copyNonAttributePropertiesFromElement(other);
}

void Element::createUniqueElementData() {
  if (!m_elementData) {
    m_elementData = UniqueElementData::create();
  } else {
    DCHECK(!m_elementData->isUnique());
    m_elementData = toShareableElementData(m_elementData)->makeUniqueCopy();
  }
}

void Element::synchronizeStyleAttributeInternal() const {
  DCHECK(isStyledElement());
  DCHECK(elementData());
  DCHECK(elementData()->m_styleAttributeIsDirty);
  elementData()->m_styleAttributeIsDirty = false;
  const StylePropertySet* inlineStyle = this->inlineStyle();
  const_cast<Element*>(this)->setSynchronizedLazyAttribute(
      styleAttr, inlineStyle ? AtomicString(inlineStyle->asText()) : nullAtom);
}

CSSStyleDeclaration* Element::style() {
  if (!isStyledElement())
    return nullptr;
  return &ensureElementRareData().ensureInlineCSSStyleDeclaration(this);
}

StylePropertyMap* Element::styleMap() {
  if (!isStyledElement())
    return nullptr;
  return &ensureElementRareData().ensureInlineStylePropertyMap(this);
}

MutableStylePropertySet& Element::ensureMutableInlineStyle() {
  DCHECK(isStyledElement());
  Member<StylePropertySet>& inlineStyle =
      ensureUniqueElementData().m_inlineStyle;
  if (!inlineStyle) {
    CSSParserMode mode = (!isHTMLElement() || document().inQuirksMode())
                             ? HTMLQuirksMode
                             : HTMLStandardMode;
    inlineStyle = MutableStylePropertySet::create(mode);
  } else if (!inlineStyle->isMutable()) {
    inlineStyle = inlineStyle->mutableCopy();
  }
  return *toMutableStylePropertySet(inlineStyle);
}

void Element::clearMutableInlineStyleIfEmpty() {
  if (ensureMutableInlineStyle().isEmpty()) {
    ensureUniqueElementData().m_inlineStyle.clear();
  }
}

inline void Element::setInlineStyleFromString(
    const AtomicString& newStyleString) {
  DCHECK(isStyledElement());
  Member<StylePropertySet>& inlineStyle = elementData()->m_inlineStyle;

  // Avoid redundant work if we're using shared attribute data with already
  // parsed inline style.
  if (inlineStyle && !elementData()->isUnique())
    return;

  // We reconstruct the property set instead of mutating if there is no CSSOM
  // wrapper.  This makes wrapperless property sets immutable and so cacheable.
  if (inlineStyle && !inlineStyle->isMutable())
    inlineStyle.clear();

  if (!inlineStyle) {
    inlineStyle = CSSParser::parseInlineStyleDeclaration(newStyleString, this);
  } else {
    DCHECK(inlineStyle->isMutable());
    static_cast<MutableStylePropertySet*>(inlineStyle.get())
        ->parseDeclarationList(newStyleString,
                               document().elementSheet().contents());
  }
}

void Element::styleAttributeChanged(
    const AtomicString& newStyleString,
    AttributeModificationReason modificationReason) {
  DCHECK(isStyledElement());
  WTF::OrdinalNumber startLineNumber = WTF::OrdinalNumber::beforeFirst();
  if (document().scriptableDocumentParser() && !document().isInDocumentWrite())
    startLineNumber = document().scriptableDocumentParser()->lineNumber();

  if (newStyleString.isNull()) {
    ensureUniqueElementData().m_inlineStyle.clear();
  } else if (modificationReason == ModifiedByCloning ||
             ContentSecurityPolicy::shouldBypassMainWorld(&document()) ||
             (containingShadowRoot() &&
              containingShadowRoot()->type() == ShadowRootType::UserAgent) ||
             document().contentSecurityPolicy()->allowInlineStyle(
                 document().url(), String(), startLineNumber, newStyleString)) {
    setInlineStyleFromString(newStyleString);
  }

  elementData()->m_styleAttributeIsDirty = false;

  setNeedsStyleRecalc(
      LocalStyleChange,
      StyleChangeReasonForTracing::create(StyleChangeReason::StyleSheetChange));
  InspectorInstrumentation::didInvalidateStyleAttr(this);
}

void Element::inlineStyleChanged() {
  DCHECK(isStyledElement());
  setNeedsStyleRecalc(LocalStyleChange, StyleChangeReasonForTracing::create(
                                            StyleChangeReason::Inline));
  DCHECK(elementData());
  elementData()->m_styleAttributeIsDirty = true;
  InspectorInstrumentation::didInvalidateStyleAttr(this);

  if (MutationObserverInterestGroup* recipients =
          MutationObserverInterestGroup::createForAttributesMutation(
              *this, styleAttr)) {
    // We don't use getAttribute() here to get a style attribute value
    // before the change.
    AtomicString oldValue;
    if (const Attribute* attribute =
            elementData()->attributes().find(styleAttr))
      oldValue = attribute->value();
    recipients->enqueueMutationRecord(
        MutationRecord::createAttributes(this, styleAttr, oldValue));
    // Need to synchronize every time so that following MutationRecords will
    // have correct oldValues.
    synchronizeAttribute(styleAttr);
  }
}

void Element::setInlineStyleProperty(CSSPropertyID propertyID,
                                     CSSValueID identifier,
                                     bool important) {
  setInlineStyleProperty(propertyID, CSSIdentifierValue::create(identifier),
                         important);
}

void Element::setInlineStyleProperty(CSSPropertyID propertyID,
                                     double value,
                                     CSSPrimitiveValue::UnitType unit,
                                     bool important) {
  setInlineStyleProperty(propertyID, CSSPrimitiveValue::create(value, unit),
                         important);
}

void Element::setInlineStyleProperty(CSSPropertyID propertyID,
                                     const CSSValue* value,
                                     bool important) {
  DCHECK(isStyledElement());
  ensureMutableInlineStyle().setProperty(propertyID, *value, important);
  inlineStyleChanged();
}

bool Element::setInlineStyleProperty(CSSPropertyID propertyID,
                                     const String& value,
                                     bool important) {
  DCHECK(isStyledElement());
  bool changes = ensureMutableInlineStyle().setProperty(
      propertyID, value, important, document().elementSheet().contents());
  if (changes)
    inlineStyleChanged();
  return changes;
}

bool Element::removeInlineStyleProperty(CSSPropertyID propertyID) {
  DCHECK(isStyledElement());
  if (!inlineStyle())
    return false;
  bool changes = ensureMutableInlineStyle().removeProperty(propertyID);
  if (changes)
    inlineStyleChanged();
  return changes;
}

void Element::removeAllInlineStyleProperties() {
  DCHECK(isStyledElement());
  if (!inlineStyle())
    return;
  ensureMutableInlineStyle().clear();
  inlineStyleChanged();
}

void Element::updatePresentationAttributeStyle() {
  synchronizeAllAttributes();
  // ShareableElementData doesn't store presentation attribute style, so make
  // sure we have a UniqueElementData.
  UniqueElementData& elementData = ensureUniqueElementData();
  elementData.m_presentationAttributeStyleIsDirty = false;
  elementData.m_presentationAttributeStyle =
      computePresentationAttributeStyle(*this);
}

void Element::addPropertyToPresentationAttributeStyle(
    MutableStylePropertySet* style,
    CSSPropertyID propertyID,
    CSSValueID identifier) {
  DCHECK(isStyledElement());
  style->setProperty(propertyID, *CSSIdentifierValue::create(identifier));
}

void Element::addPropertyToPresentationAttributeStyle(
    MutableStylePropertySet* style,
    CSSPropertyID propertyID,
    double value,
    CSSPrimitiveValue::UnitType unit) {
  DCHECK(isStyledElement());
  style->setProperty(propertyID, *CSSPrimitiveValue::create(value, unit));
}

void Element::addPropertyToPresentationAttributeStyle(
    MutableStylePropertySet* style,
    CSSPropertyID propertyID,
    const String& value) {
  DCHECK(isStyledElement());
  style->setProperty(propertyID, value, false);
}

void Element::addPropertyToPresentationAttributeStyle(
    MutableStylePropertySet* style,
    CSSPropertyID propertyID,
    const CSSValue* value) {
  DCHECK(isStyledElement());
  style->setProperty(propertyID, *value);
}

bool Element::supportsStyleSharing() const {
  if (!isStyledElement() || !parentOrShadowHostElement())
    return false;
  // If the element has inline style it is probably unique.
  if (inlineStyle())
    return false;
  if (isSVGElement() && toSVGElement(this)->animatedSMILStyleProperties())
    return false;
  // Ids stop style sharing if they show up in the stylesheets.
  if (hasID() &&
      document().ensureStyleResolver().hasRulesForId(idForStyleResolution()))
    return false;
  // :active and :hover elements always make a chain towards the document node
  // and no siblings or cousins will have the same state. There's also only one
  // :focus element per scope so we don't need to attempt to share.
  if (isUserActionElement())
    return false;
  if (!parentOrShadowHostElement()->childrenSupportStyleSharing())
    return false;
  if (this == document().cssTarget())
    return false;
  if (isHTMLElement() && toHTMLElement(this)->hasDirectionAuto())
    return false;
  // TODO(kochi): This prevents any slotted elements from sharing styles.
  // Investigate cases where we share styles to optimize styling performance.
  if (isChildOfV1ShadowHost())
    return false;
  if (hasAnimations())
    return false;
  if (Fullscreen::isCurrentFullScreenElement(*this))
    return false;
  return true;
}

void Element::logAddElementIfIsolatedWorldAndInDocument(
    const char element[],
    const QualifiedName& attr1) {
  if (!isConnected())
    return;
  V8DOMActivityLogger* activityLogger =
      V8DOMActivityLogger::currentActivityLoggerIfIsolatedWorld();
  if (!activityLogger)
    return;
  Vector<String, 2> argv;
  argv.append(element);
  argv.append(fastGetAttribute(attr1));
  activityLogger->logEvent("blinkAddElement", argv.size(), argv.data());
}

void Element::logAddElementIfIsolatedWorldAndInDocument(
    const char element[],
    const QualifiedName& attr1,
    const QualifiedName& attr2) {
  if (!isConnected())
    return;
  V8DOMActivityLogger* activityLogger =
      V8DOMActivityLogger::currentActivityLoggerIfIsolatedWorld();
  if (!activityLogger)
    return;
  Vector<String, 3> argv;
  argv.append(element);
  argv.append(fastGetAttribute(attr1));
  argv.append(fastGetAttribute(attr2));
  activityLogger->logEvent("blinkAddElement", argv.size(), argv.data());
}

void Element::logAddElementIfIsolatedWorldAndInDocument(
    const char element[],
    const QualifiedName& attr1,
    const QualifiedName& attr2,
    const QualifiedName& attr3) {
  if (!isConnected())
    return;
  V8DOMActivityLogger* activityLogger =
      V8DOMActivityLogger::currentActivityLoggerIfIsolatedWorld();
  if (!activityLogger)
    return;
  Vector<String, 4> argv;
  argv.append(element);
  argv.append(fastGetAttribute(attr1));
  argv.append(fastGetAttribute(attr2));
  argv.append(fastGetAttribute(attr3));
  activityLogger->logEvent("blinkAddElement", argv.size(), argv.data());
}

void Element::logUpdateAttributeIfIsolatedWorldAndInDocument(
    const char element[],
    const QualifiedName& attributeName,
    const AtomicString& oldValue,
    const AtomicString& newValue) {
  if (!isConnected())
    return;
  V8DOMActivityLogger* activityLogger =
      V8DOMActivityLogger::currentActivityLoggerIfIsolatedWorld();
  if (!activityLogger)
    return;
  Vector<String, 4> argv;
  argv.append(element);
  argv.append(attributeName.toString());
  argv.append(oldValue);
  argv.append(newValue);
  activityLogger->logEvent("blinkSetAttribute", argv.size(), argv.data());
}

DEFINE_TRACE(Element) {
  if (hasRareData())
    visitor->trace(elementRareData());
  visitor->trace(m_elementData);
  ContainerNode::trace(visitor);
}

DEFINE_TRACE_WRAPPERS(Element) {
  if (hasRareData()) {
    visitor->traceWrappers(elementRareData());
  }
  ContainerNode::traceWrappers(visitor);
}

}  // namespace blink