NOT FOR REVIEW - convert to cc animation

cc/animation/animation_player.h

Index: cc/animation/animation_player.h
diff --git a/cc/animation/animation_player.h b/cc/animation/animation_player.h
index 98475a602b315069d9f431ff03a7a19eaeda7c21..c93699b061e606e95b278c13a8751505d7685078 100644
--- a/cc/animation/animation_player.h
+++ b/cc/animation/animation_player.h
@@ -9,6 +9,7 @@
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/observer_list.h"
 #include "base/time/time.h"
 #include "cc/animation/animation.h"
 #include "cc/animation/animation_curve.h"
@@ -21,6 +22,7 @@ namespace cc {
 class AnimationDelegate;
 class AnimationEvents;
 class AnimationHost;
+class AnimationObserver;
 class AnimationTimeline;
 struct AnimationEvent;
 struct PropertyAnimationState;
@@ -170,6 +172,11 @@ class CC_ANIMATION_EXPORT AnimationPlayer
     return scroll_offset_animation_was_interrupted_;
   }
 
+  // This controls the list of entities who are informed of updates as
+  // animations are ticked.
+  void AddObserver(AnimationObserver* observer);
+  void RemoveObserver(AnimationObserver* observer);
+
  private:
   friend class base::RefCounted<AnimationPlayer>;
 
@@ -218,6 +225,8 @@ class CC_ANIMATION_EXPORT AnimationPlayer
 
   bool scroll_offset_animation_was_interrupted_;
 
+  base::ObserverList<AnimationObserver> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(AnimationPlayer);
 };