compositor: Tick the UI animations from cc, instead of from timer callbacks.

ui/compositor/layer_animation_delegate.h

Index: ui/compositor/layer_animation_delegate.h
diff --git a/ui/compositor/layer_animation_delegate.h b/ui/compositor/layer_animation_delegate.h
index 1d57c714fc3e551f3ac2160bf854041d3e9151a0..2f38d54819fbaa64395235728fbf9a6389cd9ee7 100644
--- a/ui/compositor/layer_animation_delegate.h
+++ b/ui/compositor/layer_animation_delegate.h
@@ -14,6 +14,8 @@
 
 namespace ui {
 
+class LayerAnimatorCollection;
+
 // Layer animations interact with the layers using this interface.
 class COMPOSITOR_EXPORT LayerAnimationDelegate {
  public:
@@ -35,6 +37,7 @@ class COMPOSITOR_EXPORT LayerAnimationDelegate {
   virtual float GetDeviceScaleFactor() const = 0;
   virtual void AddThreadedAnimation(scoped_ptr<cc::Animation> animation) = 0;
   virtual void RemoveThreadedAnimation(int animation_id) = 0;
+  virtual LayerAnimatorCollection* GetLayerAnimatorCollection() = 0;
 
  protected:
   virtual ~LayerAnimationDelegate() {}