Moves ShellObserver to ash/common

ash/app_list/app_list_presenter_delegate.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_APP_LIST_APP_LIST_PRESENTER_DELEGATE_H_
 #define ASH_APP_LIST_APP_LIST_PRESENTER_DELEGATE_H_
 
 #include <stdint.h>
 
 #include "ash/ash_export.h"
+#include "ash/common/shell_observer.h"
 #include "ash/shelf/shelf_icon_observer.h"
-#include "ash/shell_observer.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "ui/app_list/presenter/app_list_presenter_delegate.h"
 #include "ui/events/event_handler.h"
 #include "ui/keyboard/keyboard_controller_observer.h"
 
 namespace app_list {
 class ApplicationDragAndDropHost;
 class AppListPresenter;
 class AppListView;
@@ skipping 70 matching lines @@
 
   // Owned by its widget.
   app_list::AppListView* view_ = nullptr;
 
   DISALLOW_COPY_AND_ASSIGN(AppListPresenterDelegate);
 };
 
 }  // namespace ash
 
 #endif  // ASH_APP_LIST_APP_LIST_PRESENTER_DELEGATE_H_