cc: Setup API to release OutputSurface from LTHClient.

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 3dfb248c4927c894032fdcd5a0517108c6d94f2a..feb69136caef8e1e0d49768372043b55cdcbc180 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -396,6 +396,14 @@ void LayerTreeHost::SetOutputSurface(scoped_ptr<OutputSurface> surface) {
   proxy_->SetOutputSurface(surface.Pass());
 }
 
+scoped_ptr<OutputSurface> LayerTreeHost::ReleaseOutputSurface() {
+  DCHECK(!visible_);
+  DCHECK(!output_surface_lost_);
+
+  output_surface_lost_ = true;
+  return proxy_->ReleaseOutputSurface();
+}
+
 void LayerTreeHost::RequestNewOutputSurface() {
   client_->RequestNewOutputSurface();
 }