cc: Make separate interface for BeginFrame ipc from OutputSurface

cc/trees/thread_proxy.cc

Index: cc/trees/thread_proxy.cc
diff --git a/cc/trees/thread_proxy.cc b/cc/trees/thread_proxy.cc
index 34283c9212da3a798c0f11d87a5634ddbfd26058..bf36fee8ce3123da447e85a45a1a4377cc07d2c5 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -48,22 +48,27 @@ struct ThreadProxy::SchedulerStateRequest {
 scoped_ptr<Proxy> ThreadProxy::Create(
     LayerTreeHost* layer_tree_host,
     scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
-    scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner) {
-  return make_scoped_ptr(
-      new ThreadProxy(layer_tree_host, main_task_runner, impl_task_runner));
+    scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner,
+    scoped_refptr<ExternalBeginFrameSource> external_begin_frame_source) {
+  return make_scoped_ptr(new ThreadProxy(layer_tree_host,
+                                         main_task_runner,
+                                         impl_task_runner,
+                                         external_begin_frame_source));
 }
 
 ThreadProxy::ThreadProxy(
     LayerTreeHost* layer_tree_host,
     scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
-    scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner)
+    scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner,
+    scoped_refptr<ExternalBeginFrameSource> external_begin_frame_source)
     : Proxy(main_task_runner, impl_task_runner),
       main_thread_only_vars_unsafe_(this, layer_tree_host->id()),
       main_thread_or_blocked_vars_unsafe_(layer_tree_host),
       compositor_thread_vars_unsafe_(
           this,
           layer_tree_host->id(),
-          layer_tree_host->rendering_stats_instrumentation()) {
+          layer_tree_host->rendering_stats_instrumentation()),
+      external_begin_frame_source_(external_begin_frame_source) {
   TRACE_EVENT0("cc", "ThreadProxy::ThreadProxy");
   DCHECK(IsMainThread());
   DCHECK(this->layer_tree_host());
@@ -349,10 +354,6 @@ void ThreadProxy::DidSwapBuffersCompleteOnImplThread() {
       base::Bind(&ThreadProxy::DidCompleteSwapBuffers, main_thread_weak_ptr_));
 }
 
-BeginFrameSource* ThreadProxy::ExternalBeginFrameSource() {
-  return impl().layer_tree_host_impl.get();
-}
-
 void ThreadProxy::WillBeginImplFrame(const BeginFrameArgs& args) {
   impl().layer_tree_host_impl->WillBeginImplFrame(args);
 }
@@ -1183,8 +1184,12 @@ void ThreadProxy::InitializeImplOnImplThread(CompletionEvent* completion) {
   impl().scheduler = Scheduler::Create(this,
                                        scheduler_settings,
                                        impl().layer_tree_host_id,
-                                       ImplThreadTaskRunner());
+                                       ImplThreadTaskRunner(),
+                                       external_begin_frame_source_);
   impl().scheduler->SetVisible(impl().layer_tree_host_impl->visible());
+  // |external_begin_frame_source_| is not used anymore by this.
+  // Proxy only delivers |external_begin_frame_source_| to Scheduler.
+  external_begin_frame_source_ = nullptr;
 
   impl_thread_weak_ptr_ = impl().weak_factory.GetWeakPtr();
   completion->Signal();
@@ -1243,7 +1248,6 @@ void ThreadProxy::LayerTreeHostClosedOnImplThread(CompletionEvent* completion) {
   layer_tree_host()->DeleteContentsTexturesOnImplThread(
       impl().layer_tree_host_impl->resource_provider());
   impl().current_resource_update_controller = nullptr;
-  impl().layer_tree_host_impl->SetNeedsBeginFrames(false);
   impl().scheduler = nullptr;
   impl().layer_tree_host_impl = nullptr;
   impl().weak_factory.InvalidateWeakPtrs();