cc: Setup API to release OutputSurface from LTHClient.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 0d44c41ad7ca063290acce7a09744fd3cd0324af..43445c84943e0d07822e8570a72dc510275bc00e 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -2194,6 +2194,10 @@ void LayerTreeHostImpl::CleanUpTileManager() {
   single_thread_synchronous_task_graph_runner_ = nullptr;
 }
 
+scoped_ptr<OutputSurface> LayerTreeHostImpl::GetOutputSurface() {
+  return output_surface_.Pass();
+}
+
 bool LayerTreeHostImpl::InitializeRenderer(
     scoped_ptr<OutputSurface> output_surface) {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::InitializeRenderer");