cc: Post the missed BeginFrame to a new stack

cc/surfaces/display_scheduler.h

Index: cc/surfaces/display_scheduler.h
diff --git a/cc/surfaces/display_scheduler.h b/cc/surfaces/display_scheduler.h
index 16d086814225dd2d78e027bfbb6067437ad572de..87e82b5a26754e7cd04e05130a91b103858a7cbd 100644
--- a/cc/surfaces/display_scheduler.h
+++ b/cc/surfaces/display_scheduler.h
@@ -68,6 +68,9 @@ class CC_SURFACES_EXPORT DisplayScheduler : public BeginFrameObserverBase {
   base::CancelableClosure begin_frame_deadline_task_;
   base::TimeTicks begin_frame_deadline_task_time_;
 
+  base::CancelableClosure missed_begin_frame_task_;
+  bool inside_add_observer_ = false;

[sunnyps, 2016/07/27 02:00:14]

nit: TBH it's not AddObserver that we really care about, we care about being in
the middle of some state transaction and getting a BeginFrame during that.

In the scheduler we keep track of this as inside_process_scheduled_actions_.

[danakj, 2016/07/27 02:19:05]

I can call this inside_external_action_, which I've done. But IDK if that is
what you're really hoping for.

+
   bool output_surface_lost_;
   bool root_surface_resources_locked_;