ElementAnimations should hold an ObservableList of AnimationPlayers.

cc/animation/animation_player.cc

Index: cc/animation/animation_player.cc
diff --git a/cc/animation/animation_player.cc b/cc/animation/animation_player.cc
index 4cbd2a027aa23f0c8d1af605ef48d56d72a963d7..66d9b3ce73bc9a29a020ecdf21d23ec95855dda3 100644
--- a/cc/animation/animation_player.cc
+++ b/cc/animation/animation_player.cc
@@ -180,34 +180,31 @@ void AnimationPlayer::PushPropertiesTo(AnimationPlayer* player_impl) {
   }
 }
 
-void AnimationPlayer::NotifyAnimationStarted(
-    base::TimeTicks monotonic_time,
-    TargetProperty::Type target_property,
-    int group) {
+void AnimationPlayer::OnAnimationStarted(base::TimeTicks monotonic_time,
+                                         TargetProperty::Type target_property,
+                                         int group) {
   if (animation_delegate_)
     animation_delegate_->NotifyAnimationStarted(monotonic_time, target_property,
                                                 group);
 }
 
-void AnimationPlayer::NotifyAnimationFinished(
-    base::TimeTicks monotonic_time,
-    TargetProperty::Type target_property,
-    int group) {
+void AnimationPlayer::OnAnimationFinished(base::TimeTicks monotonic_time,
+                                          TargetProperty::Type target_property,
+                                          int group) {
   if (animation_delegate_)
     animation_delegate_->NotifyAnimationFinished(monotonic_time,
                                                  target_property, group);
 }
 
-void AnimationPlayer::NotifyAnimationAborted(
-    base::TimeTicks monotonic_time,
-    TargetProperty::Type target_property,
-    int group) {
+void AnimationPlayer::OnAnimationAborted(base::TimeTicks monotonic_time,
+                                         TargetProperty::Type target_property,
+                                         int group) {
   if (animation_delegate_)
     animation_delegate_->NotifyAnimationAborted(monotonic_time, target_property,
                                                 group);
 }
 
-void AnimationPlayer::NotifyAnimationTakeover(
+void AnimationPlayer::OnAnimationTakeover(
     base::TimeTicks monotonic_time,
     TargetProperty::Type target_property,
     double animation_start_time,