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 4258e9449a37dc1d2ee4375b1397269665e74c7d..1752237e69892e7a41dd3f0cbbd9029a49934b90 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);
 }
@@ -299,6 +299,7 @@ DEFINE_TRACE(AnimationTimeline) {
   visitor->Trace(timing_);
   visitor->Trace(animations_needing_update_);
   visitor->Trace(animations_);
+  SuperAnimationTimeline::Trace(visitor);
 }
 
 }  // namespace blink