ResizeObserver pt6: integration
Integrates ResizeObserver with the browser.
1) Element notifies ResizeObserver when its size might have changed.
Operations that might change Element's observed size are trapped:
Element::detachLayoutTree traps Element removal from DOM tree
LayoutObject::setMayNeedPaintInvalidation traps size changes
2) Event loop integration
FrameView::notifyResizeObserver implements it per spec.
https://wicg.github.io/ResizeObserver/#html-event-loop
3) Tests
LayoutTests/resize-observer is a comprehensive test suite.
BUG=612962
Review-Url: https://codereview.chromium.org/2204503002
Cr-Commit-Position: refs/heads/master@{#411694}
18 files changed
