mash: Move shelf model and item classes to ash/common/shelf

ash/shelf/shelf_model_observer.h

-// Copyright 2013 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_SHELF_SHELF_MODEL_OBSERVER_H_
-#define ASH_SHELF_SHELF_MODEL_OBSERVER_H_
-
-#include "ash/ash_export.h"
-#include "ash/shelf/shelf_item_types.h"
-
-namespace ash {
-
-struct ShelfItem;
-
-class ASH_EXPORT ShelfModelObserver {
- public:
-  // Invoked after an item has been added to the model.
-  virtual void ShelfItemAdded(int index) = 0;
-
-  // Invoked after an item has been removed. |index| is the index the item was
-  // at.
-  virtual void ShelfItemRemoved(int index, ShelfID id) = 0;
-
-  // Invoked after an item has been moved. See ShelfModel::Move() for details
-  // of the arguments.
-  virtual void ShelfItemMoved(int start_index, int target_index) = 0;
-
-  // Invoked when the state of an item changes. |old_item| is the item
-  // before the change.
-  virtual void ShelfItemChanged(int index, const ShelfItem& old_item) = 0;
-
- protected:
-  virtual ~ShelfModelObserver() {}
-};
-
-}  // namespace ash
-
-#endif  // ASH_SHELF_SHELF_MODEL_OBSERVER_H_