cc: Make separate interface for BeginFrame ipc from OutputSurface

cc/scheduler/scheduler.h

Index: cc/scheduler/scheduler.h
diff --git a/cc/scheduler/scheduler.h b/cc/scheduler/scheduler.h
index 2ef10a481ddebc38d8dd04dd3127f911a0285bdd..fd6cee7b8de4e259446ffaf381527f4bcb23eb40 100644
--- a/cc/scheduler/scheduler.h
+++ b/cc/scheduler/scheduler.h
@@ -32,7 +32,6 @@ namespace cc {
 
 class SchedulerClient {
  public:
-  virtual BeginFrameSource* ExternalBeginFrameSource() = 0;
   virtual void WillBeginImplFrame(const BeginFrameArgs& args) = 0;
   virtual void ScheduledActionSendBeginMainFrame() = 0;
   virtual DrawResult ScheduledActionDrawAndSwapIfPossible() = 0;
@@ -77,12 +76,14 @@ class CC_EXPORT Scheduler : public BeginFrameObserverMixIn {
       SchedulerClient* client,
       const SchedulerSettings& scheduler_settings,
       int layer_tree_host_id,
-      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner) {
+      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
+      scoped_ptr<ExternalBeginFrameSource> external_begin_frame_source) {
     SchedulerFrameSourcesConstructor frame_sources_constructor;
     return make_scoped_ptr(new Scheduler(client,
                                          scheduler_settings,
                                          layer_tree_host_id,
                                          task_runner,
+                                         external_begin_frame_source.Pass(),
                                          &frame_sources_constructor));
   }
 
@@ -164,6 +165,7 @@ class CC_EXPORT Scheduler : public BeginFrameObserverMixIn {
             const SchedulerSettings& scheduler_settings,
             int layer_tree_host_id,
             const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
+            scoped_ptr<ExternalBeginFrameSource> external_begin_frame_source,
             SchedulerFrameSourcesConstructor* frame_sources_constructor);
 
   // virtual for testing - Don't call these in the constructor or
@@ -177,6 +179,7 @@ class CC_EXPORT Scheduler : public BeginFrameObserverMixIn {
   // Storage when frame sources are internal
   scoped_ptr<BeginFrameSource> primary_frame_source_internal_;
   scoped_ptr<SyntheticBeginFrameSource> background_frame_source_internal_;
+  scoped_ptr<ExternalBeginFrameSource> external_begin_frame_source_internal_;
 
   VSyncParameterObserver* vsync_observer_;