cc : Track opacity animation changes on effect tree

cc/animation/element_animations.h

Index: cc/animation/element_animations.h
diff --git a/cc/animation/element_animations.h b/cc/animation/element_animations.h
index 04e68c26a4fc4634a12f25f42607c761dc1f2517..90d945c01cd9389e77972d5154980334f6974f60 100644
--- a/cc/animation/element_animations.h
+++ b/cc/animation/element_animations.h
@@ -229,6 +229,8 @@ class CC_EXPORT ElementAnimations : public base::RefCounted<ElementAnimations> {
 
   void UpdatePotentiallyAnimatingTransform();
 
+  bool AllOpacityAnimationsEnded();
+
   void OnFilterAnimated(ElementListType list_type,
                         const FilterOperations& filters);
   void OnOpacityAnimated(ElementListType list_type, float opacity);
@@ -239,6 +241,7 @@ class CC_EXPORT ElementAnimations : public base::RefCounted<ElementAnimations> {
   void OnAnimationWaitingForDeletion();
   void OnTransformIsPotentiallyAnimatingChanged(ElementListType list_type,
                                                 bool is_animating);
+  void OnOpacityIsCurrentlyAnimatingChanged(bool is_currently_animating);
   gfx::ScrollOffset ScrollOffsetForAnimation() const;
 
   void NotifyPlayersAnimationStarted(base::TimeTicks monotonic_time,