Adds BeginFrameControl via DevTools.

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 7d1cf0c2d283a6620d1de210bc8fc8348d66ee4d..ed39cf6881074ec4c479998fc88980239020bc19 100644
--- a/content/browser/compositor/gpu_process_transport_factory.cc
+++ b/content/browser/compositor/gpu_process_transport_factory.cc
@@ -549,7 +549,7 @@ 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.
@@ -727,6 +727,18 @@ void GpuProcessTransportFactory::SetDisplayVSyncParameters(
     data->begin_frame_source->OnUpdateVSyncParameters(timebase, interval);
 }
 
+void GpuProcessTransportFactory::SwapBeginFrameSource(
+    ui::Compositor* compositor,
+    std::unique_ptr<cc::BeginFrameSource>* begin_frame_source) {
+  PerCompositorDataMap::iterator it = per_compositor_data_.find(compositor);
+  if (it == per_compositor_data_.end())
+    return;
+  PerCompositorData* data = it->second.get();
+  DCHECK(data);
+  if (data->display)
+    data->display->SwapBeginFrameSource(begin_frame_source);
+}
+
 void GpuProcessTransportFactory::SetOutputIsSecure(ui::Compositor* compositor,
                                                    bool secure) {
   PerCompositorDataMap::iterator it = per_compositor_data_.find(compositor);