Mus Demo: Demonstrate external window mode

services/ui/demo/mus_demo_external.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SERVICES_UI_DEMO_MUS_DEMO_EXTERNAL_H_
+#define SERVICES_UI_DEMO_MUS_DEMO_EXTERNAL_H_
+
+#include <memory>
+#include <vector>
+
+#include "services/ui/demo/mus_demo.h"
+#include "services/ui/public/interfaces/window_tree_host.mojom.h"
+
+namespace ui {
+namespace demo {
+
+class MusDemoExternal : public MusDemo {
+ public:
+  MusDemoExternal();
+  ~MusDemoExternal() final;
+
+ private:
+  void OnStartImpl(std::unique_ptr<aura::WindowTreeClient>& window_tree_client,

[kylechar, 2017/02/21 15:15:10]

// MusDemo:

[kylechar, 2017/02/21 15:15:11]

I didn't notice this wasn't const in a previous CL. If you're going to be
modifying an argument it should be a pointer instead of a reference. Please
change them to be pointers or const refs.

[fwang, 2017/02/21 17:30:18]

Done. I don't really like the OnStartImpl. Note after
https://codereview.chromium.org/2700493005 we could avoid the WindowTreeData
param and just return a std::unique_ptr<aura::WindowTreeClient>, so no need to
pass ref or pointer as arguments.

+                   std::unique_ptr<WindowTreeData>& window_tree_data) final;
+
+  // aura::WindowTreeClientDelegate:
+  void OnEmbed(std::unique_ptr<aura::WindowTreeHostMus> window_tree_host) final;
+  void OnEmbedRootDestroyed(aura::WindowTreeHostMus* window_tree_host) final;
+
+  mojom::WindowTreeHostFactoryPtr window_tree_host_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(MusDemoExternal);
+};
+
+}  // namespace demo
+}  // namespace ui
+
+#endif  // SERVICES_UI_DEMO_MUS_DEMO_EXTERNAL_H_