cc: Make separate interface for BeginFrame ipc from OutputSurface

cc/trees/single_thread_proxy.cc

Index: cc/trees/single_thread_proxy.cc
diff --git a/cc/trees/single_thread_proxy.cc b/cc/trees/single_thread_proxy.cc
index 1b57b350ce4c4a4e10275c61d846f21c264b9782..f7fb32cb93519c5a9f009b331f3bf98e2b8825b4 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -23,15 +23,19 @@ namespace cc {
 scoped_ptr<Proxy> SingleThreadProxy::Create(
     LayerTreeHost* layer_tree_host,
     LayerTreeHostSingleThreadClient* client,
-    scoped_refptr<base::SingleThreadTaskRunner> main_task_runner) {
-  return make_scoped_ptr(
-      new SingleThreadProxy(layer_tree_host, client, main_task_runner));
+    scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
+    scoped_refptr<ExternalBeginFrameSource> external_begin_frame_source) {
+  return make_scoped_ptr(new SingleThreadProxy(layer_tree_host,
+                                               client,
+                                               main_task_runner,
+                                               external_begin_frame_source));
 }
 
 SingleThreadProxy::SingleThreadProxy(
     LayerTreeHost* layer_tree_host,
     LayerTreeHostSingleThreadClient* client,
-    scoped_refptr<base::SingleThreadTaskRunner> main_task_runner)
+    scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
+    scoped_refptr<ExternalBeginFrameSource> external_begin_frame_source)
     : Proxy(main_task_runner, NULL),
       layer_tree_host_(layer_tree_host),
       client_(client),
@@ -42,6 +46,7 @@ SingleThreadProxy::SingleThreadProxy(
       commit_was_deferred_(false),
       commit_requested_(false),
       output_surface_creation_requested_(false),
+      external_begin_frame_source_(external_begin_frame_source),
       weak_factory_(this) {
   TRACE_EVENT0("cc", "SingleThreadProxy::SingleThreadProxy");
   DCHECK(Proxy::IsMainThread());
@@ -83,12 +88,17 @@ void SingleThreadProxy::SetLayerTreeHostClientReady() {
   if (layer_tree_host_->settings().single_thread_proxy_scheduler &&
       !scheduler_on_impl_thread_) {
     SchedulerSettings scheduler_settings(layer_tree_host_->settings());
-    scheduler_on_impl_thread_ = Scheduler::Create(this,
-                                                  scheduler_settings,
-                                                  layer_tree_host_->id(),
-                                                  MainThreadTaskRunner());
+    scheduler_on_impl_thread_ =
+        Scheduler::Create(this,
+                          scheduler_settings,
+                          layer_tree_host_->id(),
+                          MainThreadTaskRunner(),
+                          external_begin_frame_source_);
     scheduler_on_impl_thread_->SetCanStart();
     scheduler_on_impl_thread_->SetVisible(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;
   }
 }
 
@@ -612,10 +622,6 @@ bool SingleThreadProxy::MainFrameWillHappenForTesting() {
   return false;
 }
 
-BeginFrameSource* SingleThreadProxy::ExternalBeginFrameSource() {
-  return layer_tree_host_impl_.get();
-}
-
 void SingleThreadProxy::WillBeginImplFrame(const BeginFrameArgs& args) {
   layer_tree_host_impl_->WillBeginImplFrame(args);
 }