Implement new AnimationTimeline superclass

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

Index: third_party/WebKit/Source/core/animation/AnimationTimeline.cpp
diff --git a/third_party/WebKit/Source/core/animation/AnimationTimeline.cpp b/third_party/WebKit/Source/core/animation/AnimationTimeline.cpp
index f5036c0551b350fee1d867517c9b5fecf42235e6..9470202cb8e90c62b94126962bf54b417e107142 100644
--- a/third_party/WebKit/Source/core/animation/AnimationTimeline.cpp
+++ b/third_party/WebKit/Source/core/animation/AnimationTimeline.cpp
@@ -87,7 +87,7 @@ bool AnimationTimeline::IsActive() {
 }
 
 void AnimationTimeline::AnimationAttached(Animation& animation) {
-  DCHECK_EQ(animation.timeline(), this);
+  DCHECK_EQ(animation.TimelineInternal(), this);
   DCHECK(!animations_.Contains(&animation));
   animations_.insert(&animation);
 }
@@ -322,6 +322,7 @@ DEFINE_TRACE(AnimationTimeline) {
   visitor->Trace(timing_);
   visitor->Trace(animations_needing_update_);
   visitor->Trace(animations_);
+  SuperAnimationTimeline::Trace(visitor);
 }
 
 }  // namespace blink