Blink CompositorWorker: Use CompositorElementId and CompositorIdToElementMap.

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

Index: third_party/WebKit/Source/core/animation/ElementAnimations.h
diff --git a/third_party/WebKit/Source/core/animation/ElementAnimations.h b/third_party/WebKit/Source/core/animation/ElementAnimations.h
index 2fc53486a35544c1c9986f6b111cd6fa5645135f..592b4bbac66d9a2db9e45b14eda6cca7990cb004 100644
--- a/third_party/WebKit/Source/core/animation/ElementAnimations.h
+++ b/third_party/WebKit/Source/core/animation/ElementAnimations.h
@@ -34,6 +34,7 @@
 #include "core/animation/AnimationStack.h"
 #include "core/animation/CustomCompositorAnimations.h"
 #include "core/animation/css/CSSAnimations.h"
+#include "platform/graphics/CompositorElementId.h"
 #include "wtf/HashCountedSet.h"
 #include "wtf/HashMap.h"
 #include "wtf/RefPtr.h"
@@ -79,6 +80,8 @@ public:
     void updateBaseComputedStyle(const ComputedStyle*);
     void clearBaseComputedStyle();
 
+    CompositorElementId compositorElementId() const { return m_compositorElementId; }
+
     DECLARE_TRACE();
 
 private:
@@ -88,6 +91,7 @@ private:
     CustomCompositorAnimations m_customCompositorAnimations;
     CSSAnimations m_cssAnimations;
     AnimationCountedSet m_animations;
+    const CompositorElementId m_compositorElementId;
     bool m_animationStyleChange;
     RefPtr<ComputedStyle> m_baseComputedStyle;