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

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index 3c9ea047dcd33ccac94eb190f6fc014fd5d2c77a..6efd26314e65c2bb3b7919ddf7240391cb672652 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -224,7 +224,7 @@ class COMPOSITOR_EXPORT Compositor
   // LayerTreeHostClient implementation.
   virtual void WillBeginMainFrame(int frame_id) OVERRIDE {}
   virtual void DidBeginMainFrame() OVERRIDE {}
-  virtual void Animate(base::TimeTicks frame_begin_time) OVERRIDE {}
+  virtual void Animate(base::TimeTicks frame_begin_time) OVERRIDE;
   virtual void Layout() OVERRIDE;
   virtual void ApplyScrollAndScale(const gfx::Vector2d& scroll_delta,
                                    float page_scale) OVERRIDE {}