Extract shell methods from ApplicationImpl into a base class, and pass this to Initialize() instead.

ui/views/mus/platform_window_mus.h

 // Copyright 2015 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 UI_VIEWS_MUS_PLATFORM_WINDOW_MUS_H_
 #define UI_VIEWS_MUS_PLATFORM_WINDOW_MUS_H_
 
 #include <stdint.h>
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "components/mus/public/cpp/input_event_handler.h"
 #include "components/mus/public/cpp/window_observer.h"
 #include "ui/platform_window/platform_window.h"
 #include "ui/views/mus/mus_export.h"
 
 namespace bitmap_uploader {
 class BitmapUploader;
 }
 
 namespace mojo {
-namespace shell {
-namespace mojom {
 class Shell;
 }
-}
-}
 
 namespace ui {
 class ViewProp;
 }
 
 namespace views {
 
 class VIEWS_MUS_EXPORT PlatformWindowMus
     : public NON_EXPORTED_BASE(ui::PlatformWindow),
       public mus::WindowObserver,
       public NON_EXPORTED_BASE(mus::InputEventHandler) {
  public:
   PlatformWindowMus(ui::PlatformWindowDelegate* delegate,
-                    mojo::shell::mojom::Shell* shell,
+                    mojo::Shell* shell,
                     mus::Window* mus_window);
   ~PlatformWindowMus() override;
 
   void Activate();
 
   void SetCursorById(mus::mojom::Cursor cursor);
 
   // ui::PlatformWindow:
   void Show() override;
   void Hide() override;
@@ skipping 50 matching lines @@
 #ifndef NDEBUG
   scoped_ptr<base::WeakPtrFactory<PlatformWindowMus>> weak_factory_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(PlatformWindowMus);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_MUS_PLATFORM_WINDOW_MUS_H_