Refactoring the way begin frame sources inside scheduler work.

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 53fb3843d665b7416a1ecf2dd278d6034b8f3bb6..ca8c290d2302e5446076f6e2b149e1773a9323ea 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -351,14 +351,8 @@ void ThreadProxy::DidSwapBuffersCompleteOnImplThread() {
       base::Bind(&ThreadProxy::DidCompleteSwapBuffers, main_thread_weak_ptr_));
 }
 
-void ThreadProxy::SetNeedsBeginFrame(bool enable) {
-  TRACE_EVENT1("cc", "ThreadProxy::SetNeedsBeginFrame", "enable", enable);
-  impl().layer_tree_host_impl->SetNeedsBeginFrame(enable);
-  UpdateBackgroundAnimateTicking();
-}
-
-void ThreadProxy::BeginFrame(const BeginFrameArgs& args) {
-  impl().scheduler->BeginFrame(args);
+BeginFrameSource* ThreadProxy::ExternalBeginFrameSource() {
+  return impl().layer_tree_host_impl.get();
 }
 
 void ThreadProxy::WillBeginImplFrame(const BeginFrameArgs& args) {
@@ -1252,7 +1246,7 @@ void ThreadProxy::LayerTreeHostClosedOnImplThread(CompletionEvent* completion) {
   layer_tree_host()->DeleteContentsTexturesOnImplThread(
       impl().layer_tree_host_impl->resource_provider());
   impl().current_resource_update_controller.reset();
-  impl().layer_tree_host_impl->SetNeedsBeginFrame(false);
+  impl().layer_tree_host_impl->SetNeedsBeginFrames(false);
   impl().scheduler.reset();
   impl().layer_tree_host_impl.reset();
   impl().weak_factory.InvalidateWeakPtrs();