third_party/WebKit/Source/core/css/StyleSheetContents.cpp

/*
 * (C) 1999-2003 Lars Knoll (knoll@kde.org)
 * Copyright (C) 2004, 2006, 2007, 2012 Apple Inc. All rights reserved.
 *
 * 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/css/StyleSheetContents.h"

#include "core/css/CSSPropertyValueSet.h"
#include "core/css/CSSStyleSheet.h"
#include "core/css/CSSTiming.h"
#include "core/css/StyleEngine.h"
#include "core/css/StyleRule.h"
#include "core/css/StyleRuleImport.h"
#include "core/css/StyleRuleNamespace.h"
#include "core/css/parser/CSSParser.h"
#include "core/dom/Document.h"
#include "core/dom/Node.h"
#include "core/frame/UseCounter.h"
#include "core/inspector/InspectorTraceEvents.h"
#include "core/loader/resource/CSSStyleSheetResource.h"
#include "platform/Histogram.h"
#include "platform/instrumentation/tracing/TraceEvent.h"
#include "platform/weborigin/SecurityOrigin.h"

namespace blink {

// static
const Document* StyleSheetContents::SingleOwnerDocument(
    const StyleSheetContents* style_sheet_contents) {
  // TODO(https://crbug.com/242125): We may want to handle stylesheets that have
  // multiple owners when this is used for UseCounter.
  if (style_sheet_contents && style_sheet_contents->HasSingleOwnerNode())
    return style_sheet_contents->SingleOwnerDocument();
  return nullptr;
}

// Rough size estimate for the memory cache.
unsigned StyleSheetContents::EstimatedSizeInBytes() const {
  // Note that this does not take into account size of the strings hanging from
  // various objects. The assumption is that nearly all of of them are atomic
  // and would exist anyway.
  unsigned size = sizeof(*this);

  // FIXME: This ignores the children of media rules.
  // Most rules are StyleRules.
  size += RuleCount() * StyleRule::AverageSizeInBytes();

  for (unsigned i = 0; i < import_rules_.size(); ++i) {
    if (StyleSheetContents* sheet = import_rules_[i]->GetStyleSheet())
      size += sheet->EstimatedSizeInBytes();
  }
  return size;
}

StyleSheetContents::StyleSheetContents(StyleRuleImport* owner_rule,
                                       const String& original_url,
                                       const CSSParserContext* context)
    : owner_rule_(owner_rule),
      original_url_(original_url),
      default_namespace_(g_star_atom),
      has_syntactically_valid_css_header_(true),
      did_load_error_occur_(false),
      is_mutable_(false),
      has_font_face_rule_(false),
      has_viewport_rule_(false),
      has_media_queries_(false),
      has_single_owner_document_(true),
      is_used_from_text_cache_(false),
      parser_context_(context) {}

StyleSheetContents::StyleSheetContents(const StyleSheetContents& o)
    : owner_rule_(nullptr),
      original_url_(o.original_url_),
      import_rules_(o.import_rules_.size()),
      namespace_rules_(o.namespace_rules_.size()),
      child_rules_(o.child_rules_.size()),
      namespaces_(o.namespaces_),
      default_namespace_(o.default_namespace_),
      has_syntactically_valid_css_header_(
          o.has_syntactically_valid_css_header_),
      did_load_error_occur_(false),
      is_mutable_(false),
      has_font_face_rule_(o.has_font_face_rule_),
      has_viewport_rule_(o.has_viewport_rule_),
      has_media_queries_(o.has_media_queries_),
      has_single_owner_document_(true),
      is_used_from_text_cache_(false),
      parser_context_(o.parser_context_) {
  // FIXME: Copy import rules.
  DCHECK(o.import_rules_.IsEmpty());

  for (unsigned i = 0; i < namespace_rules_.size(); ++i) {
    namespace_rules_[i] =
        static_cast<StyleRuleNamespace*>(o.namespace_rules_[i]->Copy());
  }

  // LazyParseCSS: Copying child rules is a strict point for lazy parsing, so
  // there is no need to copy lazy parsing state here.
  for (unsigned i = 0; i < child_rules_.size(); ++i)
    child_rules_[i] = o.child_rules_[i]->Copy();
}

StyleSheetContents::~StyleSheetContents() = default;

void StyleSheetContents::SetHasSyntacticallyValidCSSHeader(bool is_valid_css) {
  has_syntactically_valid_css_header_ = is_valid_css;
}

bool StyleSheetContents::IsCacheableForResource() const {
  // This would require dealing with multiple clients for load callbacks.
  if (!LoadCompleted())
    return false;
  if (has_media_queries_ &&
      !RuntimeEnabledFeatures::CacheStyleSheetWithMediaQueriesEnabled())
    return false;
  // FIXME: Support copying import rules.
  if (!import_rules_.IsEmpty())
    return false;
  // FIXME: Support cached stylesheets in import rules.
  if (owner_rule_)
    return false;
  if (did_load_error_occur_)
    return false;
  // It is not the original sheet anymore.
  if (is_mutable_)
    return false;
  // If the header is valid we are not going to need to check the
  // SecurityOrigin.
  // FIXME: Valid mime type avoids the check too.
  if (!has_syntactically_valid_css_header_)
    return false;
  return true;
}

bool StyleSheetContents::IsCacheableForStyleElement() const {
  // FIXME: Support copying import rules.
  if (!ImportRules().IsEmpty())
    return false;
  // Until import rules are supported in cached sheets it's not possible for
  // loading to fail.
  DCHECK(!DidLoadErrorOccur());
  // It is not the original sheet anymore.
  if (IsMutable())
    return false;
  if (!HasSyntacticallyValidCSSHeader())
    return false;
  return true;
}

void StyleSheetContents::ParserAppendRule(StyleRuleBase* rule) {
  if (rule->IsImportRule()) {
    // Parser enforces that @import rules come before anything else
    DCHECK(child_rules_.IsEmpty());
    StyleRuleImport* import_rule = ToStyleRuleImport(rule);
    if (import_rule->MediaQueries())
      SetHasMediaQueries();
    import_rules_.push_back(import_rule);
    import_rules_.back()->SetParentStyleSheet(this);
    import_rules_.back()->RequestStyleSheet();
    return;
  }

  if (rule->IsNamespaceRule()) {
    // Parser enforces that @namespace rules come before all rules other than
    // import/charset rules
    DCHECK(child_rules_.IsEmpty());
    StyleRuleNamespace& namespace_rule = ToStyleRuleNamespace(*rule);
    ParserAddNamespace(namespace_rule.Prefix(), namespace_rule.Uri());
    namespace_rules_.push_back(&namespace_rule);
    return;
  }

  child_rules_.push_back(rule);
}

void StyleSheetContents::SetHasMediaQueries() {
  has_media_queries_ = true;
  if (ParentStyleSheet())
    ParentStyleSheet()->SetHasMediaQueries();
}

StyleRuleBase* StyleSheetContents::RuleAt(unsigned index) const {
  SECURITY_DCHECK(index < RuleCount());

  if (index < import_rules_.size())
    return import_rules_[index].Get();

  index -= import_rules_.size();

  if (index < namespace_rules_.size())
    return namespace_rules_[index].Get();

  index -= namespace_rules_.size();

  return child_rules_[index].Get();
}

unsigned StyleSheetContents::RuleCount() const {
  return import_rules_.size() + namespace_rules_.size() + child_rules_.size();
}

void StyleSheetContents::ClearRules() {
  for (unsigned i = 0; i < import_rules_.size(); ++i) {
    DCHECK_EQ(import_rules_.at(i)->ParentStyleSheet(), this);
    import_rules_[i]->ClearParentStyleSheet();
  }
  import_rules_.clear();
  namespace_rules_.clear();
  child_rules_.clear();
}

bool StyleSheetContents::WrapperInsertRule(StyleRuleBase* rule,
                                           unsigned index) {
  DCHECK(is_mutable_);
  SECURITY_DCHECK(index <= RuleCount());

  if (index < import_rules_.size() ||
      (index == import_rules_.size() && rule->IsImportRule())) {
    // Inserting non-import rule before @import is not allowed.
    if (!rule->IsImportRule())
      return false;

    StyleRuleImport* import_rule = ToStyleRuleImport(rule);
    if (import_rule->MediaQueries())
      SetHasMediaQueries();

    import_rules_.insert(index, import_rule);
    import_rules_[index]->SetParentStyleSheet(this);
    import_rules_[index]->RequestStyleSheet();
    // FIXME: Stylesheet doesn't actually change meaningfully before the
    // imported sheets are loaded.
    return true;
  }
  // Inserting @import rule after a non-import rule is not allowed.
  if (rule->IsImportRule())
    return false;

  index -= import_rules_.size();

  if (index < namespace_rules_.size() ||
      (index == namespace_rules_.size() && rule->IsNamespaceRule())) {
    // Inserting non-namespace rules other than import rule before @namespace is
    // not allowed.
    if (!rule->IsNamespaceRule())
      return false;
    // Inserting @namespace rule when rules other than import/namespace/charset
    // are present is not allowed.
    if (!child_rules_.IsEmpty())
      return false;

    StyleRuleNamespace* namespace_rule = ToStyleRuleNamespace(rule);
    namespace_rules_.insert(index, namespace_rule);
    // For now to be compatible with IE and Firefox if namespace rule with same
    // prefix is added irrespective of adding the rule at any index, last added
    // rule's value is considered.
    // TODO (ramya.v@samsung.com): As per spec last valid rule should be
    // considered, which means if namespace rule is added in the middle of
    // existing namespace rules, rule which comes later in rule list with same
    // prefix needs to be considered.
    ParserAddNamespace(namespace_rule->Prefix(), namespace_rule->Uri());
    return true;
  }

  if (rule->IsNamespaceRule())
    return false;

  index -= namespace_rules_.size();

  child_rules_.insert(index, rule);
  return true;
}

bool StyleSheetContents::WrapperDeleteRule(unsigned index) {
  DCHECK(is_mutable_);
  SECURITY_DCHECK(index < RuleCount());

  if (index < import_rules_.size()) {
    import_rules_[index]->ClearParentStyleSheet();
    if (import_rules_[index]->IsFontFaceRule())
      NotifyRemoveFontFaceRule(ToStyleRuleFontFace(import_rules_[index].Get()));
    import_rules_.EraseAt(index);
    return true;
  }
  index -= import_rules_.size();

  if (index < namespace_rules_.size()) {
    if (!child_rules_.IsEmpty())
      return false;
    namespace_rules_.EraseAt(index);
    return true;
  }
  index -= namespace_rules_.size();

  if (child_rules_[index]->IsFontFaceRule())
    NotifyRemoveFontFaceRule(ToStyleRuleFontFace(child_rules_[index].Get()));
  child_rules_.EraseAt(index);
  return true;
}

void StyleSheetContents::ParserAddNamespace(const AtomicString& prefix,
                                            const AtomicString& uri) {
  DCHECK(!uri.IsNull());
  if (prefix.IsNull()) {
    default_namespace_ = uri;
    return;
  }
  PrefixNamespaceURIMap::AddResult result = namespaces_.insert(prefix, uri);
  if (result.is_new_entry)
    return;
  result.stored_value->value = uri;
}

const AtomicString& StyleSheetContents::NamespaceURIFromPrefix(
    const AtomicString& prefix) const {
  return namespaces_.at(prefix);
}

void StyleSheetContents::ParseAuthorStyleSheet(
    const CSSStyleSheetResource* cached_style_sheet,
    const SecurityOrigin* security_origin) {
  TRACE_EVENT1("blink,devtools.timeline", "ParseAuthorStyleSheet", "data",
               InspectorParseAuthorStyleSheetEvent::Data(cached_style_sheet));
  double start_time = MonotonicallyIncreasingTime();

  bool is_same_origin_request =
      security_origin && security_origin->CanRequest(BaseURL());

  // When the response was fetched via the Service Worker, the original URL may
  // not be same as the base URL.
  // TODO(horo): When we will use the original URL as the base URL, we can
  // remove this check. crbug.com/553535
  if (is_same_origin_request &&
      cached_style_sheet->GetResponse().WasFetchedViaServiceWorker()) {
    const KURL original_url(
        cached_style_sheet->GetResponse().OriginalURLViaServiceWorker());
    // |originalURL| is empty when the response is created in the SW.
    if (!original_url.IsEmpty() && !security_origin->CanRequest(original_url))
      is_same_origin_request = false;
  }

  CSSStyleSheetResource::MIMETypeCheck mime_type_check =
      IsQuirksModeBehavior(parser_context_->Mode()) && is_same_origin_request
          ? CSSStyleSheetResource::MIMETypeCheck::kLax
          : CSSStyleSheetResource::MIMETypeCheck::kStrict;
  String sheet_text =
      cached_style_sheet->SheetText(parser_context_, mime_type_check);

  const ResourceResponse& response = cached_style_sheet->GetResponse();
  source_map_url_ = response.HttpHeaderField(HTTPNames::SourceMap);
  if (source_map_url_.IsEmpty()) {
    // Try to get deprecated header.
    source_map_url_ = response.HttpHeaderField(HTTPNames::X_SourceMap);
  }

  const CSSParserContext* context =
      CSSParserContext::CreateWithStyleSheetContents(ParserContext(), this);
  CSSParser::ParseSheet(context, this, sheet_text,
                        RuntimeEnabledFeatures::LazyParseCSSEnabled());

  DEFINE_STATIC_LOCAL(CustomCountHistogram, parse_histogram,
                      ("Style.AuthorStyleSheet.ParseTime", 0, 10000000, 50));
  double parse_duration_seconds = (MonotonicallyIncreasingTime() - start_time);
  parse_histogram.Count(parse_duration_seconds * 1000 * 1000);
  if (Document* document = SingleOwnerDocument()) {
    CSSTiming::From(*document).RecordAuthorStyleSheetParseTime(
        parse_duration_seconds);
  }
}

void StyleSheetContents::ParseString(const String& sheet_text) {
  ParseStringAtPosition(sheet_text, TextPosition::MinimumPosition());
}

void StyleSheetContents::ParseStringAtPosition(
    const String& sheet_text,
    const TextPosition& start_position) {
  const CSSParserContext* context =
      CSSParserContext::CreateWithStyleSheetContents(ParserContext(), this);
  CSSParser::ParseSheet(context, this, sheet_text);
}

bool StyleSheetContents::IsLoading() const {
  for (unsigned i = 0; i < import_rules_.size(); ++i) {
    if (import_rules_[i]->IsLoading())
      return true;
  }
  return false;
}

bool StyleSheetContents::LoadCompleted() const {
  StyleSheetContents* parent_sheet = ParentStyleSheet();
  if (parent_sheet)
    return parent_sheet->LoadCompleted();

  StyleSheetContents* root = RootStyleSheet();
  return root->loading_clients_.IsEmpty();
}

void StyleSheetContents::CheckLoaded() {
  if (IsLoading())
    return;

  StyleSheetContents* parent_sheet = ParentStyleSheet();
  if (parent_sheet) {
    parent_sheet->CheckLoaded();
    return;
  }

  DCHECK_EQ(this, RootStyleSheet());
  if (loading_clients_.IsEmpty())
    return;

  // Avoid |CSSSStyleSheet| and |OwnerNode| being deleted by scripts that run
  // via ScriptableDocumentParser::ExecuteScriptsWaitingForResources(). Also
  // protect the |CSSStyleSheet| from being deleted during iteration via the
  // |SheetLoaded| method.
  //
  // When a sheet is loaded it is moved from the set of loading clients
  // to the set of completed clients. We therefore need the copy in order to
  // not modify the set while iterating it.
  HeapVector<Member<CSSStyleSheet>> loading_clients;
  CopyToVector(loading_clients_, loading_clients);

  for (unsigned i = 0; i < loading_clients.size(); ++i) {
    if (loading_clients[i]->LoadCompleted())
      continue;

    // sheetLoaded might be invoked after its owner node is removed from
    // document.
    if (Node* owner_node = loading_clients[i]->ownerNode()) {
      if (loading_clients[i]->SheetLoaded())
        owner_node->NotifyLoadedSheetAndAllCriticalSubresources(
            did_load_error_occur_ ? Node::kErrorOccurredLoadingSubresource
                                  : Node::kNoErrorLoadingSubresource);
    }
  }
}

void StyleSheetContents::NotifyLoadedSheet(const CSSStyleSheetResource* sheet) {
  DCHECK(sheet);
  did_load_error_occur_ |= sheet->ErrorOccurred();
  // updateLayoutIgnorePendingStyleSheets can cause us to create the RuleSet on
  // this sheet before its imports have loaded. So clear the RuleSet when the
  // imports load since the import's subrules are flattened into its parent
  // sheet's RuleSet.
  ClearRuleSet();
}

void StyleSheetContents::StartLoadingDynamicSheet() {
  StyleSheetContents* root = RootStyleSheet();
  for (const auto& client : root->loading_clients_)
    client->StartLoadingDynamicSheet();
  // Copy the completed clients to a vector for iteration.
  // startLoadingDynamicSheet will move the style sheet from the completed state
  // to the loading state which modifies the set of completed clients. We
  // therefore need the copy in order to not modify the set of completed clients
  // while iterating it.
  HeapVector<Member<CSSStyleSheet>> completed_clients;
  CopyToVector(root->completed_clients_, completed_clients);
  for (unsigned i = 0; i < completed_clients.size(); ++i)
    completed_clients[i]->StartLoadingDynamicSheet();
}

StyleSheetContents* StyleSheetContents::RootStyleSheet() const {
  const StyleSheetContents* root = this;
  while (root->ParentStyleSheet())
    root = root->ParentStyleSheet();
  return const_cast<StyleSheetContents*>(root);
}

bool StyleSheetContents::HasSingleOwnerNode() const {
  return RootStyleSheet()->HasOneClient();
}

Node* StyleSheetContents::SingleOwnerNode() const {
  StyleSheetContents* root = RootStyleSheet();
  if (!root->HasOneClient())
    return nullptr;
  if (root->loading_clients_.size())
    return (*root->loading_clients_.begin())->ownerNode();
  return (*root->completed_clients_.begin())->ownerNode();
}

Document* StyleSheetContents::SingleOwnerDocument() const {
  StyleSheetContents* root = RootStyleSheet();
  return root->ClientSingleOwnerDocument();
}

Document* StyleSheetContents::AnyOwnerDocument() const {
  return RootStyleSheet()->ClientAnyOwnerDocument();
}

static bool ChildRulesHaveFailedOrCanceledSubresources(
    const HeapVector<Member<StyleRuleBase>>& rules) {
  for (unsigned i = 0; i < rules.size(); ++i) {
    const StyleRuleBase* rule = rules[i].Get();
    switch (rule->GetType()) {
      case StyleRuleBase::kStyle:
        if (ToStyleRule(rule)->PropertiesHaveFailedOrCanceledSubresources())
          return true;
        break;
      case StyleRuleBase::kFontFace:
        if (ToStyleRuleFontFace(rule)
                ->Properties()
                .HasFailedOrCanceledSubresources())
          return true;
        break;
      case StyleRuleBase::kMedia:
        if (ChildRulesHaveFailedOrCanceledSubresources(
                ToStyleRuleMedia(rule)->ChildRules()))
          return true;
        break;
      case StyleRuleBase::kCharset:
      case StyleRuleBase::kImport:
      case StyleRuleBase::kNamespace:
        NOTREACHED();
      case StyleRuleBase::kPage:
      case StyleRuleBase::kKeyframes:
      case StyleRuleBase::kKeyframe:
      case StyleRuleBase::kSupports:
      case StyleRuleBase::kViewport:
        break;
    }
  }
  return false;
}

bool StyleSheetContents::HasFailedOrCanceledSubresources() const {
  DCHECK(IsCacheableForResource());
  return ChildRulesHaveFailedOrCanceledSubresources(child_rules_);
}

Document* StyleSheetContents::ClientAnyOwnerDocument() const {
  if (ClientSize() <= 0)
    return nullptr;
  if (loading_clients_.size())
    return (*loading_clients_.begin())->OwnerDocument();
  return (*completed_clients_.begin())->OwnerDocument();
}

Document* StyleSheetContents::ClientSingleOwnerDocument() const {
  return has_single_owner_document_ ? ClientAnyOwnerDocument() : nullptr;
}

StyleSheetContents* StyleSheetContents::ParentStyleSheet() const {
  return owner_rule_ ? owner_rule_->ParentStyleSheet() : nullptr;
}

void StyleSheetContents::RegisterClient(CSSStyleSheet* sheet) {
  DCHECK(!loading_clients_.Contains(sheet));
  DCHECK(!completed_clients_.Contains(sheet));

  // InspectorCSSAgent::BuildObjectForRule creates CSSStyleSheet without any
  // owner node.
  if (!sheet->OwnerDocument())
    return;

  if (Document* document = ClientSingleOwnerDocument()) {
    if (sheet->OwnerDocument() != document)
      has_single_owner_document_ = false;
  }
  loading_clients_.insert(sheet);
}

void StyleSheetContents::UnregisterClient(CSSStyleSheet* sheet) {
  loading_clients_.erase(sheet);
  completed_clients_.erase(sheet);

  if (!sheet->OwnerDocument() || !loading_clients_.IsEmpty() ||
      !completed_clients_.IsEmpty())
    return;

  has_single_owner_document_ = true;
}

void StyleSheetContents::ClientLoadCompleted(CSSStyleSheet* sheet) {
  DCHECK(loading_clients_.Contains(sheet) || !sheet->OwnerDocument());
  loading_clients_.erase(sheet);
  // In owner_node_->SheetLoaded, the CSSStyleSheet might be detached.
  // (i.e. ClearOwnerNode was invoked.)
  // In this case, we don't need to add the stylesheet to completed clients.
  if (!sheet->OwnerDocument())
    return;
  completed_clients_.insert(sheet);
}

void StyleSheetContents::ClientLoadStarted(CSSStyleSheet* sheet) {
  DCHECK(completed_clients_.Contains(sheet));
  completed_clients_.erase(sheet);
  loading_clients_.insert(sheet);
}

void StyleSheetContents::SetReferencedFromResource(
    CSSStyleSheetResource* resource) {
  DCHECK(resource);
  DCHECK(!IsReferencedFromResource());
  DCHECK(IsCacheableForResource());
  referenced_from_resource_ = resource;
}

void StyleSheetContents::ClearReferencedFromResource() {
  DCHECK(IsReferencedFromResource());
  DCHECK(IsCacheableForResource());
  referenced_from_resource_ = nullptr;
}

RuleSet& StyleSheetContents::EnsureRuleSet(const MediaQueryEvaluator& medium,
                                           AddRuleFlags add_rule_flags) {
  if (!rule_set_) {
    rule_set_ = RuleSet::Create();
    rule_set_->AddRulesFromSheet(this, medium, add_rule_flags);
  }
  return *rule_set_.Get();
}

static void SetNeedsActiveStyleUpdateForClients(
    HeapHashSet<WeakMember<CSSStyleSheet>>& clients) {
  for (const auto& sheet : clients) {
    Document* document = sheet->OwnerDocument();
    Node* node = sheet->ownerNode();
    if (!document || !node || !node->isConnected())
      continue;
    document->GetStyleEngine().SetNeedsActiveStyleUpdate(node->GetTreeScope());
  }
}

void StyleSheetContents::ClearRuleSet() {
  if (StyleSheetContents* parent_sheet = ParentStyleSheet())
    parent_sheet->ClearRuleSet();

  if (!rule_set_)
    return;

  rule_set_.Clear();
  SetNeedsActiveStyleUpdateForClients(loading_clients_);
  SetNeedsActiveStyleUpdateForClients(completed_clients_);
}

static void RemoveFontFaceRules(HeapHashSet<WeakMember<CSSStyleSheet>>& clients,
                                const StyleRuleFontFace* font_face_rule) {
  for (const auto& sheet : clients) {
    if (Node* owner_node = sheet->ownerNode())
      owner_node->GetDocument().GetStyleEngine().RemoveFontFaceRules(
          HeapVector<Member<const StyleRuleFontFace>>(1, font_face_rule));
  }
}

void StyleSheetContents::NotifyRemoveFontFaceRule(
    const StyleRuleFontFace* font_face_rule) {
  StyleSheetContents* root = RootStyleSheet();
  RemoveFontFaceRules(root->loading_clients_, font_face_rule);
  RemoveFontFaceRules(root->completed_clients_, font_face_rule);
}

static void FindFontFaceRulesFromRules(
    const HeapVector<Member<StyleRuleBase>>& rules,
    HeapVector<Member<const StyleRuleFontFace>>& font_face_rules) {
  for (unsigned i = 0; i < rules.size(); ++i) {
    StyleRuleBase* rule = rules[i].Get();

    if (rule->IsFontFaceRule()) {
      font_face_rules.push_back(ToStyleRuleFontFace(rule));
    } else if (rule->IsMediaRule()) {
      StyleRuleMedia* media_rule = ToStyleRuleMedia(rule);
      // We cannot know whether the media rule matches or not, but
      // for safety, remove @font-face in the media rule (if exists).
      FindFontFaceRulesFromRules(media_rule->ChildRules(), font_face_rules);
    }
  }
}

void StyleSheetContents::FindFontFaceRules(
    HeapVector<Member<const StyleRuleFontFace>>& font_face_rules) {
  for (unsigned i = 0; i < import_rules_.size(); ++i) {
    if (!import_rules_[i]->GetStyleSheet())
      continue;
    import_rules_[i]->GetStyleSheet()->FindFontFaceRules(font_face_rules);
  }

  FindFontFaceRulesFromRules(ChildRules(), font_face_rules);
}

void StyleSheetContents::Trace(blink::Visitor* visitor) {
  visitor->Trace(owner_rule_);
  visitor->Trace(import_rules_);
  visitor->Trace(namespace_rules_);
  visitor->Trace(child_rules_);
  visitor->Trace(loading_clients_);
  visitor->Trace(completed_clients_);
  visitor->Trace(rule_set_);
  visitor->Trace(referenced_from_resource_);
  visitor->Trace(parser_context_);
}

}  // namespace blink