Blink CompositorWorker: Use CompositorElementId and CompositorIdToElementMap.

third_party/WebKit/Source/core/animation/ElementAnimations.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 16 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "core/animation/ElementAnimations.h"
 
 #include "core/layout/LayoutObject.h"
 
 namespace blink {
 
+static CompositorElementId s_nextCompositorElementId = 1;

[esprehn, 2016/05/10 22:46:57]

You should use DOMNodeIds, why can't you allocate an id the first time someone
needs to read ElementAnimations::elementId() ?

Compositor animations are pretty rare all things considered. You can just do:

if (!m_id)
  m_id = DOMNodeIds::add(m_element)
return m_id;

[loyso (OOO), 2016/05/12 05:55:39]

Not every Compositor Animation subsystem has associated Element. See
ScrollAnimatorCompositorCoordinator.cpp and LinkHighlightImpl.cpp in the
dependent CL.

+
 ElementAnimations::ElementAnimations()
-    : m_animationStyleChange(false)
+    : m_compositorElementId(s_nextCompositorElementId++)
+    , m_animationStyleChange(false)
 {
 }
 
 ElementAnimations::~ElementAnimations()
 {
 }
 
 void ElementAnimations::updateAnimationFlags(ComputedStyle& style)
 {
     for (const auto& entry : m_animations) {
@@ skipping 73 matching lines @@
     // TODO(rune@opera.com): The FontFaceCache version number may be increased without forcing
     // a style recalc (see crbug.com/471079). ComputedStyle objects created with different cache
     // versions will not be considered equal as Font::operator== will compare versions, hence
     // ComputedStyle::operator== will return false. We avoid using baseComputedStyle (the check for
     // isFallbackValid()) in that case to avoid triggering the ComputedStyle comparison ASSERT
     // in updateBaseComputedStyle.
     return m_animationStyleChange && (!m_baseComputedStyle || m_baseComputedStyle->font().isFallbackValid());
 }
 
 } // namespace blink