Unified BeginFrame scheduling

cc/scheduler/scheduler_state_machine.h

Index: cc/scheduler/scheduler_state_machine.h
diff --git a/cc/scheduler/scheduler_state_machine.h b/cc/scheduler/scheduler_state_machine.h
index d92a352f236af27058d8068174c8bd2d04092ac0..a175854b76a91e1ebf1e499b6cefa9b3258b26e2 100644
--- a/cc/scheduler/scheduler_state_machine.h
+++ b/cc/scheduler/scheduler_state_machine.h
@@ -235,6 +235,9 @@ class CC_EXPORT SchedulerStateMachine {
     continuous_painting_ = continuous_painting;
   }
 
+  void SetChildrenNeedBeginFrames(bool children_need_begin_frames);
+  bool children_need_begin_frames() { return children_need_begin_frames_; }
+
  protected:
   bool BeginFrameNeededToAnimateOrDraw() const;
   bool ProactiveBeginFrameWanted() const;
@@ -305,6 +308,7 @@ class CC_EXPORT SchedulerStateMachine {
   bool skip_next_begin_main_frame_to_reduce_latency_;
   bool skip_begin_main_frame_to_reduce_latency_;
   bool continuous_painting_;
+  bool children_need_begin_frames_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);