cc: Create ProxyBeginFrameSource

cc/trees/layer_tree_host_client.h

Index: cc/trees/layer_tree_host_client.h
diff --git a/cc/trees/layer_tree_host_client.h b/cc/trees/layer_tree_host_client.h
index ac025f2ef7078b8ed8a4def8ae35715ba6f08627..996e10299c8a789545acc3d8e7083140af5187fb 100644
--- a/cc/trees/layer_tree_host_client.h
+++ b/cc/trees/layer_tree_host_client.h
@@ -52,10 +52,6 @@ class LayerTreeHostClient {
   // Called when page scale animation has completed.
   virtual void DidCompletePageScaleAnimation() = 0;
 
-  // TODO(simonhong): Makes this to pure virtual function when client
-  // implementation is ready.
-  virtual void SendBeginFramesToChildren(const BeginFrameArgs& args) {}
-
   // Requests that the client insert a rate limiting token in the shared main
   // thread context's command stream that will block if the context gets too far
   // ahead of the compositor's command stream. Only needed if the tree contains