Mus Demo: Refactor code to prepare multiple windows in external mode

services/ui/demo/mus_demo_internal.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_INTERNAL_H_
 #define SERVICES_UI_DEMO_MUS_DEMO_INTERNAL_H_
 
 #include <map>
 #include <memory>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "services/ui/demo/mus_demo.h"
 #include "ui/aura/mus/window_manager_delegate.h"
 
 namespace ui {
 namespace demo {
 
 // MusDemoInternal demonstrates Mus operating in "internal" mode: There is a
 // single acceleratedWidget for a single display and all aura windows are
 // contained in that display.
 class MusDemoInternal : public MusDemo, public aura::WindowManagerDelegate {
  public:
   MusDemoInternal();
   ~MusDemoInternal() final;
 
  private:
   // ui::demo::MusDemo:
-  void OnStartImpl(std::unique_ptr<aura::WindowTreeClient>* window_tree_client,
-                   std::unique_ptr<WindowTreeData>* window_tree_data) final;
+  void OnStartImpl() final;
+  std::unique_ptr<aura::WindowTreeClient> CreateWindowTreeClient() final;
 
   // aura::WindowManagerDelegate:
   void SetWindowManagerClient(aura::WindowManagerClient* client) final;
   bool OnWmSetBounds(aura::Window* window, gfx::Rect* bounds) final;
   bool OnWmSetProperty(aura::Window* window,
                        const std::string& name,
                        std::unique_ptr<std::vector<uint8_t>>* new_data) final;
   void OnWmSetCanFocus(aura::Window* window, bool can_focus) final;
   aura::Window* OnWmCreateTopLevelWindow(
       ui::mojom::WindowType window_type,
@@ skipping 19 matching lines @@
   bool IsWindowActive(aura::Window* window) final;
   void OnWmDeactivateWindow(aura::Window* window) final;
 
   DISALLOW_COPY_AND_ASSIGN(MusDemoInternal);
 };
 
 }  // namespace demo
 }  // namespace ui
 
 #endif  // SERVICES_UI_DEMO_MUS_DEMO_INTERNAL_H_