cc: Implement unified BeginFrame on aura

cc/scheduler/scheduler.h

Index: cc/scheduler/scheduler.h
diff --git a/cc/scheduler/scheduler.h b/cc/scheduler/scheduler.h
index ef52ccf9f7b780a74ebe2b2119d7da451b28110b..647df6f20a1117907e07d46e872bfff8ce704853 100644
--- a/cc/scheduler/scheduler.h
+++ b/cc/scheduler/scheduler.h
@@ -169,6 +169,7 @@ class CC_EXPORT Scheduler : public BeginFrameObserverMixIn,
   }
 
   void SetChildrenNeedBeginFrames(bool children_need_begin_frames);
+  void SetAuthoritativeVSyncInterval(base::TimeDelta interval);
 
  protected:
   Scheduler(SchedulerClient* client,
@@ -192,6 +193,7 @@ class CC_EXPORT Scheduler : public BeginFrameObserverMixIn,
   scoped_ptr<SyntheticBeginFrameSource> background_frame_source_internal_;
 
   VSyncParameterObserver* vsync_observer_;
+  base::TimeDelta authoritative_vsync_interval_;
 
   const SchedulerSettings settings_;
   SchedulerClient* client_;