cc: Always use SetNeedsBeginFrame to request the next BeginFrame

cc/output/output_surface.cc

Index: cc/output/output_surface.cc
diff --git a/cc/output/output_surface.cc b/cc/output/output_surface.cc
index 2ffcf95901f8885463802adeb584ef27c739847b..eada9815a1e672973937868e3dfeed58e33361a3 100644
--- a/cc/output/output_surface.cc
+++ b/cc/output/output_surface.cc
@@ -192,7 +192,6 @@ void OutputSurface::CheckForRetroactiveBeginFrame() {
 }
 
 void OutputSurface::DidSwapBuffers() {
-  begin_frame_pending_ = false;

[enne (OOO), 2013/09/13 17:48:44]

Pardon my ongoing confusion, but I still can't wrap my head around what
begin_frame_pending_ is supposed to mean.  I think I see what it's doing, but I
can't get past the naming.

begin_frame_pending_ seems to imply that BeginFrame has been sent from
OutputSurface to the Scheduler and that the Scheduler is not ready for another
one until another OutputSurface::SetNeedsBeginFrame(true) has been called.  So
it almost seems like !begin_frame_pending_ is equivalent to
client_ready_for_begin_frame_?

[brianderson, 2013/09/13 18:24:46]

Your understand is correct.  begin_frame_pending_ is an ambiguous name since it
might refer to the BeginFrame message, the emulated BeginFrame, or the client's
BeginFrame.  client_ready_for_begin_frame_ sounds like an excellent replacement.

   pending_swap_buffers_++;
   TRACE_EVENT1("cc", "OutputSurface::DidSwapBuffers",
                "pending_swap_buffers_", pending_swap_buffers_);