ash::ShelfView: CHECK against potentially bad static_casts.

ash/shelf/shelf_view.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_SHELF_SHELF_VIEW_H_
 #define ASH_SHELF_SHELF_VIEW_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 338 matching lines @@
   OverflowBubble* owner_overflow_bubble_;
 
   scoped_ptr<ShelfTooltipManager> tooltip_;
 
   // Pointer device that initiated the current drag operation. If there is no
   // current dragging operation, this is NONE.
   Pointer drag_pointer_;
 
   // The view being dragged. This is set immediately when the mouse is pressed.
   // |dragging_| is set only if the mouse is dragged far enough.
-  views::View* drag_view_;
+  ShelfButton* drag_view_;
 
   // Position of the mouse down event in |drag_view_|'s coordinates.
   gfx::Point drag_origin_;
 
   // Index |drag_view_| was initially at.
   int start_drag_index_;
 
   // Used for the context menu of a particular item.
   ShelfID context_menu_id_;
 
@@ skipping 69 matching lines @@
 
   // True when ripped item from overflow bubble is entered into Shelf.
   bool dragged_off_from_overflow_to_shelf_;
 
   DISALLOW_COPY_AND_ASSIGN(ShelfView);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELF_SHELF_VIEW_H_