Mus Demo: Demonstrate external window mode

services/ui/demo/mus_demo_internal.h

Index: services/ui/demo/mus_demo_internal.h
diff --git a/services/ui/demo/mus_demo_internal.h b/services/ui/demo/mus_demo_internal.h
index c486c16f096bf8bb6630441bc2e5205562c5e6be..d5f873974d570a36dd887af5cbe1d29b4e1c379d 100644
--- a/services/ui/demo/mus_demo_internal.h
+++ b/services/ui/demo/mus_demo_internal.h
@@ -23,8 +23,9 @@ class MusDemoInternal : public MusDemo, public aura::WindowManagerDelegate {
   ~MusDemoInternal() final;
 
  private:
-  void OnStartImpl(std::unique_ptr<aura::WindowTreeClient>& window_tree_client,
-                   std::unique_ptr<WindowTreeData>& window_tree_data) final;
+  // ui::demo::MusDemo:
+  void OnStartImpl(std::unique_ptr<aura::WindowTreeClient>* window_tree_client,
+                   std::unique_ptr<WindowTreeData>* window_tree_data) final;
 
   // aura::WindowManagerDelegate:
   void SetWindowManagerClient(aura::WindowManagerClient* client) final;