cc: Emulate BeginFrame in OutputSurfaces that don't support it natively

cc/scheduler/scheduler.h

Index: cc/scheduler/scheduler.h
diff --git a/cc/scheduler/scheduler.h b/cc/scheduler/scheduler.h
index aec0cdf2b56dcb4e801f41af44f165831ae3205d..48b4e387ae2fea61b1ba1ee51f4404eccf8c3c64 100644
--- a/cc/scheduler/scheduler.h
+++ b/cc/scheduler/scheduler.h
@@ -33,6 +33,7 @@ struct ScheduledActionDrawAndSwapResult {
 
 class SchedulerClient {
  public:
+  virtual void SetNeedsBeginFrameOnImplThread(bool enable) = 0;
   virtual void ScheduledActionSendBeginFrameToMainThread() = 0;
   virtual ScheduledActionDrawAndSwapResult
   ScheduledActionDrawAndSwapIfPossible() = 0;
@@ -49,14 +50,13 @@ class SchedulerClient {
   virtual ~SchedulerClient() {}
 };
 
-class CC_EXPORT Scheduler : FrameRateControllerClient {
+class CC_EXPORT Scheduler {
  public:
   static scoped_ptr<Scheduler> Create(
       SchedulerClient* client,
-      scoped_ptr<FrameRateController> frame_rate_controller,
-      const SchedulerSettings& scheduler_settings) {
-    return make_scoped_ptr(new Scheduler(
-        client, frame_rate_controller.Pass(), scheduler_settings));
+      const SchedulerSettings& scheduler_settings,
+      Thread* thread) {

[nduca, 2013/06/04 04:53:59]

So, typically the only thing in cc that gets to post tasks is thread proxy... 
want to share some thoughts on this? This is sorta the reason why I was
suggested making the output surface impl do the task posting logic.

[brianderson, 2013/06/04 18:33:27]

That sounds like a good restriction to have. I brought the Thread in because it
used to be used by the DelayBasedTimeSource, but that no longer exists here.

When we add deadlines in a future patch, we could have the OutputSurface do the
task posting logic (although the OutputSurface also doesn't have access to the
Thread). For now though, I think I will add a
SchedulerClient::RequestBeginFrameRetry so Scheduler doesn't need to know about
the Thread and task posting.

+    return make_scoped_ptr(new Scheduler(client,  scheduler_settings, thread));
   }
 
   virtual ~Scheduler();
@@ -86,13 +86,6 @@ class CC_EXPORT Scheduler : FrameRateControllerClient {
   void FinishCommit();
   void BeginFrameAbortedByMainThread();
 
-  void SetMaxFramesPending(int max);
-  int MaxFramesPending() const;
-  int NumFramesPendingForTesting() const;
-
-  void SetSwapBuffersCompleteSupported(bool supported);
-  void DidSwapBuffersComplete();
-
   void DidLoseOutputSurface();
   void DidCreateAndInitializeOutputSurface();
   bool HasInitializedOutputSurface() const {
@@ -104,28 +97,37 @@ class CC_EXPORT Scheduler : FrameRateControllerClient {
 
   bool WillDrawIfNeeded() const;
 
-  void SetTimebaseAndInterval(base::TimeTicks timebase,
-                              base::TimeDelta interval);
-
   base::TimeTicks AnticipatedDrawTime();
 
   base::TimeTicks LastBeginFrameOnImplThreadTime();
 
-  // FrameRateControllerClient implementation
-  virtual void BeginFrame(bool throttled) OVERRIDE;
+  void BeginFrame(base::TimeTicks frame_time);

[nduca, 2013/06/04 04:53:59]

an explanation of what these mean would be good. I haven't quite figured them
out yet.

[brianderson, 2013/06/04 18:33:27]

Added the following comments:

  // BeginFrame gets called when we should produce a frame.
  // Each BeginFrame will have a corresponding swap.
  void BeginFrame(base::TimeTicks frame_time);

  // BeginFrame will not get called again until we swap.
  // We use BeginFrameRetry to retry a BeginFrame that hasn't yet swapped.
  // TODO(brianderson): Allow the scheduler to request a new BeginFrame
  // without swapping.
  void BeginFrameRetry();

+  void BeginFrameRetry();
 
   std::string StateAsStringForTesting() { return state_machine_.ToString(); }
 
  private:
   Scheduler(SchedulerClient* client,
-            scoped_ptr<FrameRateController> frame_rate_controller,
-            const SchedulerSettings& scheduler_settings);
+            const SchedulerSettings& scheduler_settings,
+            Thread* thread);
 
+  void SetupNextBeginFrameIfNeeded();
+  void DrawAndSwapIfPossible();
+  void DrawAndSwapForced();
   void ProcessScheduledActions();
 
   const SchedulerSettings settings_;
   SchedulerClient* client_;
-  scoped_ptr<FrameRateController> frame_rate_controller_;
+
+  base::WeakPtrFactory<Scheduler> weak_factory_;
+  Thread* thread_;
+  bool last_set_needs_begin_frame_;
+  int pending_begin_frames_;
+  int incomplete_swaps_;

[nduca, 2013/06/04 04:53:59]

what are incomplete swaps?

[brianderson, 2013/06/04 18:33:27]

This should go away. I was using this to debug the checkerboarding I saw and
forgot to remove it.

+  base::TimeTicks last_begin_frame_time_;
+  base::TimeTicks anticipated_draw_time_;

[nduca, 2013/06/04 04:53:59]

this is the deadline, right? Calling it anticipated is a bit funky since it
implies to me a sort of yes or we might be later. 

[brianderson, 2013/06/04 18:33:27]

The variable corresponds to the AnticipatedDrawTime member function. We haven't
added the concept of a deadline yet, so I would like to stay away from using
that naming for now. It is a kind of deadline though: the scheduler will try to
draw at that time, but it might not if not needed.

+  base::TimeDelta interval_;
+
   SchedulerStateMachine state_machine_;
   bool inside_process_scheduled_actions_;