CC Animations: Port UI Browser Compositor to use compositor animation timelines.

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index 1602d30caae8b7b4ad72f727422e309428722004..6c3c07d514c8a1a927c2527e6f4184ddd1535385 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -33,6 +33,7 @@ class SingleThreadTaskRunner;
 }
 
 namespace cc {
+class AnimationTimeline;
 class ContextProvider;
 class Layer;
 class LayerTreeDebugState;
@@ -177,6 +178,8 @@ class COMPOSITOR_EXPORT Compositor
   Layer* root_layer() { return root_layer_; }
   void SetRootLayer(Layer* root_layer);
 
+  cc::AnimationTimeline* GetAnimationTimeline() const;
+
   // Called when we need the compositor to preserve the alpha channel in the
   // output for situations when we want to render transparently atop something
   // else, e.g. Aero glass.
@@ -368,6 +371,7 @@ class COMPOSITOR_EXPORT Compositor
   CompositorLock* compositor_lock_;
 
   LayerAnimatorCollection layer_animator_collection_;
+  scoped_refptr<cc::AnimationTimeline> animation_timeline_;
 
   // Used to send to any new CompositorBeginFrameObserver immediately.
   cc::BeginFrameArgs missed_begin_frame_args_;