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..51816bca1fb288021e89b01c9291584e74033ee4 100644
--- a/cc/scheduler/scheduler_state_machine.h
+++ b/cc/scheduler/scheduler_state_machine.h
@@ -235,8 +235,12 @@ 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 BeginFrameNeededToChildren() const;
   bool ProactiveBeginFrameWanted() const;
 
   // True if we need to force activations to make forward progress.
@@ -305,6 +309,7 @@ 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);