cc: Make separate interface for BeginFrame ipc from OutputSurface

cc/trees/layer_tree_host.h

Index: cc/trees/layer_tree_host.h
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index 10964160bb5b8ea74f8eec716747f96d0c5a8f06..bf2835efd952df25c1bf78a3ffbe157e1f7e38ad 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -47,6 +47,7 @@ class GpuMemoryBufferManager;
 
 namespace cc {
 class AnimationRegistrar;
+class BeginFrameSource;
 class HeadsUpDisplayLayer;
 class Layer;
 class LayerTreeHostImpl;
@@ -91,7 +92,8 @@ class CC_EXPORT LayerTreeHost {
       gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager,
       const LayerTreeSettings& settings,
       scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
-      scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner);
+      scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner,
+      scoped_ptr<BeginFrameSource> external_begin_frame_source);
 
   static scoped_ptr<LayerTreeHost> CreateSingleThreaded(
       LayerTreeHostClient* client,
@@ -99,7 +101,8 @@ class CC_EXPORT LayerTreeHost {
       SharedBitmapManager* shared_bitmap_manager,
       gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager,
       const LayerTreeSettings& settings,
-      scoped_refptr<base::SingleThreadTaskRunner> main_task_runner);
+      scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
+      scoped_ptr<BeginFrameSource> external_begin_frame_source);
   virtual ~LayerTreeHost();
 
   void SetLayerTreeHostClientReady();
@@ -314,10 +317,12 @@ class CC_EXPORT LayerTreeHost {
                 const LayerTreeSettings& settings);
   void InitializeThreaded(
       scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
-      scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner);
+      scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner,
+      scoped_ptr<BeginFrameSource> external_begin_frame_source);
   void InitializeSingleThreaded(
       LayerTreeHostSingleThreadClient* single_thread_client,
-      scoped_refptr<base::SingleThreadTaskRunner> main_task_runner);
+      scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
+      scoped_ptr<BeginFrameSource> external_begin_frame_source);
   void InitializeForTesting(scoped_ptr<Proxy> proxy_for_testing);
   void SetOutputSurfaceLostForTesting(bool is_lost) {
     output_surface_lost_ = is_lost;