cc: Setup API to release OutputSurface from LTHClient.

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 bf03378246811e78226c911a557a513f4843223d..7190cccd11eed21fef9a3e52c3d29590e14e2543 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -149,6 +149,10 @@ void SingleThreadProxy::RequestNewOutputSurface() {
   layer_tree_host_->RequestNewOutputSurface();
 }
 
+scoped_ptr<OutputSurface> SingleThreadProxy::GetOutputSurface() {
+  return layer_tree_host_impl_->GetOutputSurface();
+}
+
 void SingleThreadProxy::SetOutputSurface(
     scoped_ptr<OutputSurface> output_surface) {
   DCHECK(Proxy::IsMainThread());