cc: Handle retroactive BeginFrames in the Scheduler.

cc/scheduler/scheduler.h

Index: cc/scheduler/scheduler.h
diff --git a/cc/scheduler/scheduler.h b/cc/scheduler/scheduler.h
index 7d577b0187ac334a9324f407990121a2f082eeb2..3f139c617839f2d33bca2de987d0dd748dc55532 100644
--- a/cc/scheduler/scheduler.h
+++ b/cc/scheduler/scheduler.h
@@ -24,7 +24,8 @@ class Thread;
 
 class SchedulerClient {
  public:
-  virtual void SetNeedsBeginImplFrame(bool enable) = 0;
+  virtual void SetNeedsBeginFrame(bool enable) = 0;
+  virtual void OnBeginImplFrame(const BeginFrameArgs& args) = 0;
   virtual void ScheduledActionSendBeginMainFrame() = 0;
   virtual DrawSwapReadbackResult ScheduledActionDrawAndSwapIfPossible() = 0;
   virtual DrawSwapReadbackResult ScheduledActionDrawAndSwapForced() = 0;
@@ -110,7 +111,9 @@ class CC_EXPORT Scheduler {
 
   base::TimeTicks LastBeginImplFrameTime();
 
-  void BeginImplFrame(const BeginFrameArgs& args);
+  void BeginFrame(const BeginFrameArgs& args);
+  void BeginRetroFrame();
+  void BeginImplFrame();
   void OnBeginImplFrameDeadline();
   void PollForAnticipatedDrawTriggers();
 
@@ -130,7 +133,7 @@ class CC_EXPORT Scheduler {
 
   base::TimeTicks AdjustedBeginImplFrameDeadline() const;
   void ScheduleBeginImplFrameDeadline(base::TimeTicks deadline);
-  void SetupNextBeginImplFrameIfNeeded();
+  void SetupNextBeginFrameIfNeeded();
   void ActivatePendingTree();
   void DrawAndSwapIfPossible();
   void DrawAndSwapForced();
@@ -147,8 +150,13 @@ class CC_EXPORT Scheduler {
   int layer_tree_host_id_;
   scoped_refptr<base::SequencedTaskRunner> impl_task_runner_;
 
-  bool last_set_needs_begin_impl_frame_;
-  BeginFrameArgs last_begin_impl_frame_args_;
+  bool last_set_needs_begin_frame_;
+  bool begin_retro_frame_posted_;
+
+  BeginFrameArgs begin_frame_args_;

[Sami, 2014/04/01 13:09:10]

It seems like we could do without this field and instead pass the args to
BeginImplFrame etc. directly. Not sure if it's clearer than what we have now,
but it might make the data flow easier to see. WDYT?

[brianderson, 2014/04/01 19:12:53]

I liked the idea of having access to the original BeginFrame deadline in
addition to the adjusted BeginImplFrame deadline.

I'll change begin_frame_args_ to a deque, which will make the data flow very
explicit and also make long deadlines easier to implement in the future.

[brianderson, 2014/04/02 04:15:57]

I ended up getting rid of begin_frame_args_ like you suggested. We can store it
if we need it in the future. I still created a deque of begin_retro_frame_args
though.

+  BeginFrameArgs begin_retro_frame_args_;
+  BeginFrameArgs begin_impl_frame_args_;
+
   base::CancelableClosure begin_impl_frame_deadline_closure_;
   base::CancelableClosure poll_for_draw_triggers_closure_;
   base::RepeatingTimer<Scheduler> advance_commit_state_timer_;