cc: Allow SendBeginMainFrame in idle state for synchronous compositor.

cc/scheduler/scheduler_state_machine.cc

Index: cc/scheduler/scheduler_state_machine.cc
diff --git a/cc/scheduler/scheduler_state_machine.cc b/cc/scheduler/scheduler_state_machine.cc
index 9dd65511669916003de3cc8cab5acbb66bc2682b..4faa9116118bcee718e986fab8cc0a2620f2cde8 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -26,11 +26,11 @@ SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
       last_frame_number_swap_requested_(-1),
       last_frame_number_begin_main_frame_sent_(-1),
       last_frame_number_invalidate_output_surface_performed_(-1),
-      animate_funnel_(false),
-      request_swap_funnel_(false),
-      send_begin_main_frame_funnel_(false),
-      invalidate_output_surface_funnel_(false),
-      prepare_tiles_funnel_(0),
+      animate_funnel_(true),
+      request_swap_funnel_(true),
+      send_begin_main_frame_funnel_(true),
+      invalidate_output_surface_funnel_(true),
+      prepare_tiles_funnel_(1),

[mithro-old, 2015/07/08 03:26:33]

Why do these values change?

[sunnyps, 2015/07/13 23:56:11]

Only the value for send_begin_main_frame_funnel_ needs to change. The basic idea
is this: for webview we want to allow SendBeginMainFrame in the
BEGIN_IMPL_FRAME_STATE_IDLE state in between frames. However we do not want to
allow SendBeginMainFrame before we've received the first BeginFrame in a "run"
of BeginFrames. To do that we set the funnel to true initially and also when we
end a run of frames and to false on each new frame (as before).

       consecutive_checkerboard_animations_(0),
       max_pending_swaps_(1),
       pending_swaps_(0),
@@ -421,7 +421,8 @@ bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
   if (!CouldSendBeginMainFrame())
     return false;
 
-  // Do not send begin main frame too many times in a single frame.
+  // Do not send begin main frame too many times in a single frame or before
+  // the first BeginFrame.
   if (send_begin_main_frame_funnel_)
     return false;
 
@@ -439,14 +440,16 @@ bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
     return false;
   }
 
-  // We should not send BeginMainFrame while we are in
-  // BEGIN_IMPL_FRAME_STATE_IDLE since we might have new
-  // user input arriving soon.
+  // We should not send BeginMainFrame while we are in the idle state since we
+  // might have new user input arriving soon. It's okay to send BeginMainFrame
+  // for the synchronous compositor because the main thread is always high
+  // latency in that case.
   // TODO(brianderson): Allow sending BeginMainFrame while idle when the main
-  // thread isn't consuming user input.
-  if (begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_IDLE &&
-      BeginFrameNeeded())
+  // thread isn't consuming user input for non-synchronous compositor.
+  if (!settings_.using_synchronous_renderer_compositor &&
+      begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_IDLE) {
     return false;
+  }
 
   // We need a new commit for the forced redraw. This honors the
   // single commit per interval because the result will be swapped to screen.