Keep vsync enabled while there is a pending requestAnimationFrame

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 55581a457232b46732f098f4a912712cb5331f81..f73576bbad87552ba2e2f61ec84143086565ac01 100644
--- a/cc/scheduler/scheduler_state_machine.h
+++ b/cc/scheduler/scheduler_state_machine.h
@@ -102,6 +102,8 @@ class CC_EXPORT SchedulerStateMachine {
   // thread to main.
   void SetNeedsCommit();
 
+  void SetAnimateRequested();
+
   // As SetNeedsCommit(), but ensures the BeginFrame will definitely happen even
   // if we are not visible.  After this call we expect to go through the forced
   // commit flow and then return to waiting for a non-forced BeginFrame to
@@ -185,6 +187,7 @@ class CC_EXPORT SchedulerStateMachine {
   bool can_draw_;
   bool has_pending_tree_;
   bool draw_if_possible_failed_;
+  bool animate_requested_;
   TextureState texture_state_;
   OutputSurfaceState output_surface_state_;