Convert //ash from scoped_ptr to std::unique_ptr

ash/wm/stacking_controller.h

 // Copyright (c) 2012 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 ASH_WM_STACKING_CONTROLLER_H_
 #define ASH_WM_STACKING_CONTROLLER_H_
 
 #include "ash/ash_export.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
-#include "base/memory/scoped_ptr.h"
 #include "ui/aura/client/window_tree_client.h"
 
 namespace ash {
 class AlwaysOnTopController;
 
 class ASH_EXPORT StackingController : public aura::client::WindowTreeClient {
  public:
   StackingController();
   ~StackingController() override;
 
@@ skipping 10 matching lines @@
   // placed in the screen lock modal container.
   aura::Window* GetSystemModalContainer(aura::Window* root,
                                         aura::Window* window) const;
 
   DISALLOW_COPY_AND_ASSIGN(StackingController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_STACKING_CONTROLLER_H_