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

ui/views/mus/screen_mus.h

 // Copyright 2016 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_SCREEN_MUS_H_
 #define UI_VIEWS_MUS_SCREEN_MUS_H_
 
 #include <vector>
 
 #include "base/observer_list.h"
 #include "components/mus/public/interfaces/display.mojom.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/screen.h"
 #include "ui/views/mus/mus_export.h"
 
 namespace mojo {
-class ApplicationImpl;
+class Shell;
 }
 
 namespace views {
 
 class ScreenMusDelegate;
 
 // Screen implementation backed by mus::mojom::DisplayManager.
 class VIEWS_MUS_EXPORT ScreenMus
     : public gfx::Screen,
       public NON_EXPORTED_BASE(mus::mojom::DisplayManagerObserver) {
  public:
   explicit ScreenMus(ScreenMusDelegate* delegate);
   ~ScreenMus() override;
 
-  void Init(mojo::ApplicationImpl* app);
+  void Init(mojo::Shell* shell);
 
  private:
   int FindDisplayIndexById(int64_t id) const;
 
   // Invoked when a display changed in some weay, including being added.
   // If |is_primary| is true, |changed_display| is the primary display.
   void ProcessDisplayChanged(const gfx::Display& changed_display,
                              bool is_primary);
 
   // gfx::Screen:
@@ skipping 21 matching lines @@
   mojo::Binding<mus::mojom::DisplayManagerObserver>
       display_manager_observer_binding_;
   base::ObserverList<gfx::DisplayObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenMus);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_MUS_SCREEN_MUS_H_