cc: Poll for state that triggers draws (synchronous compositor only)

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 aaefa37bc67bad6c2634d8b62a3c44bd59a64c57..cc48257e62fd3692c85f0d5dcf6411590198b281 100644
--- a/cc/scheduler/scheduler_state_machine.h
+++ b/cc/scheduler/scheduler_state_machine.h
@@ -121,6 +121,11 @@ class CC_EXPORT SchedulerStateMachine {
   void DidLeaveBeginFrame();
   bool inside_begin_frame() const { return inside_begin_frame_; }
 
+  // PollForAnticipatedDrawTriggers is used by the synchronous compositor to
+  // avoid requesting BeginImplFrames when we won't actually draw but still
+  // need to advance our state at vsync intervals.
+  void PollForAnticipatedDrawTriggers();
+
   // Indicates whether the LayerTreeHostImpl is visible.
   void SetVisible(bool visible);