Implement aura::WindowPortMus::CreateCompositorFrameSink()

ui/aura/mus/window_tree_client.cc

Index: ui/aura/mus/window_tree_client.cc
diff --git a/ui/aura/mus/window_tree_client.cc b/ui/aura/mus/window_tree_client.cc
index 5244c70da3aab0a8c2835aa8be5d51270b5e3e41..ef062fc415af85dc385e37593af5a6714ec8e9d2 100644
--- a/ui/aura/mus/window_tree_client.cc
+++ b/ui/aura/mus/window_tree_client.cc
@@ -947,6 +947,11 @@ void WindowTreeClient::StopPointerWatcher() {
   has_pointer_watcher_ = false;
 }
 
+void WindowTreeClient::GetFrameSinkId(Id window_id) {
+  DCHECK(tree_);
+  tree_->GetFrameSinkId(window_id);
+}
+
 void WindowTreeClient::AddObserver(WindowTreeClientObserver* observer) {
   observers_.AddObserver(observer);
 }