cc: Make separate interface for BeginFrame ipc from OutputSurface

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index bbc52882caf8d6a5e42909d1ce2c947ab5feae68..df6240c50bf2845bffb18ca0decc7c56e839af80 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -32,6 +32,7 @@
 #include "content/common/content_switches_internal.h"
 #include "content/common/gpu/client/context_provider_command_buffer.h"
 #include "content/public/common/content_switches.h"
+#include "content/renderer/gpu/compositor_external_begin_frame_source.h"
 #include "content/renderer/input/input_handler_manager.h"
 #include "content/renderer/render_thread_impl.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
@@ -535,20 +536,27 @@ void RenderWidgetCompositor::Initialize(cc::LayerTreeSettings settings) {
     main_thread_compositor_task_runner =
         render_thread->main_thread_compositor_task_runner();
   }
+  scoped_ptr<CompositorExternalBeginFrameSource> external_begin_frame_source;
+  if (settings.begin_frame_scheduling_enabled) {
+    external_begin_frame_source.reset(new CompositorExternalBeginFrameSource(
+        widget_->routing_id()));
+  }
   if (compositor_message_loop_proxy.get()) {
     layer_tree_host_ =
         cc::LayerTreeHost::CreateThreaded(this,
                                           shared_bitmap_manager,
                                           settings,
                                           main_thread_compositor_task_runner,
-                                          compositor_message_loop_proxy);
+                                          compositor_message_loop_proxy,
+                                          external_begin_frame_source.Pass());
   } else {
     layer_tree_host_ = cc::LayerTreeHost::CreateSingleThreaded(
         this,
         this,
         shared_bitmap_manager,
         settings,
-        main_thread_compositor_task_runner);
+        main_thread_compositor_task_runner,
+        external_begin_frame_source.Pass());
   }
   DCHECK(layer_tree_host_);
 }