cc: Setup API to release OutputSurface from LTHClient.

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 a528e3eb3d1b5c7905a845ce2a7a82218a8ef122..33339119e52f7a3f7f04f938e0649d0262af1ba1 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -219,6 +219,10 @@ void ThreadProxy::SetOutputSurface(scoped_ptr<OutputSurface> output_surface) {
                  impl_thread_weak_ptr_, base::Passed(&output_surface)));
 }
 
+scoped_ptr<OutputSurface> ThreadProxy::GetOutputSurface() {
+  return impl().layer_tree_host_impl->GetOutputSurface();
+}
+
 void ThreadProxy::DidInitializeOutputSurface(
     bool success,
     const RendererCapabilities& capabilities) {