cc: Introduce BeginFrame sequence numbers and acknowledgements.

content/browser/compositor/gpu_process_transport_factory.cc

Index: content/browser/compositor/gpu_process_transport_factory.cc
diff --git a/content/browser/compositor/gpu_process_transport_factory.cc b/content/browser/compositor/gpu_process_transport_factory.cc
index 23c4cbd818916f0f8586f6be37f7d3157ba92522..200277905dc6844acae0e877e2c1f0787a9384b5 100644
--- a/content/browser/compositor/gpu_process_transport_factory.cc
+++ b/content/browser/compositor/gpu_process_transport_factory.cc
@@ -436,16 +436,18 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
     }
   }
 
-  std::unique_ptr<cc::SyntheticBeginFrameSource> begin_frame_source;
+  cc::SyntheticBeginFrameSource* synthetic_begin_frame_source;
   if (!compositor->GetRendererSettings().disable_display_vsync) {
-    begin_frame_source.reset(new cc::DelayBasedBeginFrameSource(
+    synthetic_begin_frame_source = new cc::DelayBasedBeginFrameSource(
         base::MakeUnique<cc::DelayBasedTimeSource>(
-            compositor->task_runner().get())));
+            compositor->task_runner().get()));
   } else {
-    begin_frame_source.reset(new cc::BackToBackBeginFrameSource(
+    synthetic_begin_frame_source = new cc::BackToBackBeginFrameSource(
         base::MakeUnique<cc::DelayBasedTimeSource>(
-            compositor->task_runner().get())));
+            compositor->task_runner().get()));
   }
+  std::unique_ptr<cc::BeginFrameSource> begin_frame_source(
+      synthetic_begin_frame_source);
 
   BrowserCompositorOutputSurface::UpdateVSyncParametersCallback vsync_callback =
       base::Bind(&ui::Compositor::SetDisplayVSyncParameters, compositor);
@@ -510,10 +512,11 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
                   context_provider, vsync_callback, std::move(validator));
         } else {
 #if defined(USE_AURA)
+          std::unique_ptr<MusBrowserCompositorOutputSurface> mus_output_surface;
           if (compositor->window()) {
             // TODO(mfomitchev): Remove this clause once we complete the switch
             // to Aura-Mus.
-            display_output_surface =
+            mus_output_surface =
                 base::MakeUnique<MusBrowserCompositorOutputSurface>(
                     compositor->window(), context_provider,
                     GetGpuMemoryBufferManager(), vsync_callback,
@@ -522,12 +525,18 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
             aura::WindowTreeHost* host =
                 aura::WindowTreeHost::GetForAcceleratedWidget(
                     compositor->widget());
-            display_output_surface =
+            mus_output_surface =
                 base::MakeUnique<MusBrowserCompositorOutputSurface>(
                     host->window(), context_provider,
                     GetGpuMemoryBufferManager(), vsync_callback,
                     std::move(validator));
           }
+          // We use the ExternalBeginFrameSource provided by the output surface
+          // instead of our own synthetic one.
+          begin_frame_source.reset(new cc::DelegatingBeginFrameSource(
+              mus_output_surface->GetBeginFrameSource()));
+          synthetic_begin_frame_source = nullptr;
+          display_output_surface = std::move(mus_output_surface);
 #else
           NOTREACHED();
 #endif
@@ -537,7 +546,8 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
   }
 
   data->display_output_surface = display_output_surface.get();
-  data->begin_frame_source = begin_frame_source.get();
+  if (synthetic_begin_frame_source)
+    data->begin_frame_source = synthetic_begin_frame_source;
   if (data->reflector)
     data->reflector->OnSourceSurfaceReady(data->display_output_surface);
 
@@ -547,7 +557,7 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
 #endif
 
   std::unique_ptr<cc::DisplayScheduler> scheduler(new cc::DisplayScheduler(
-      begin_frame_source.get(), compositor->task_runner().get(),
+      compositor->task_runner().get(),
       display_output_surface->capabilities().max_frames_pending));
 
   // The Display owns and uses the |display_output_surface| created above.