views: Make MenuDelegate constructor virtual.

views/controls/menu/menu_delegate.h

 // Copyright (c) 2011 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 VIEWS_CONTROLS_MENU_MENU_DELEGATE_H_
 #define VIEWS_CONTROLS_MENU_MENU_DELEGATE_H_
 #pragma once
 
 #include <set>
 #include <string>
@@ skipping 33 matching lines @@
     // Indicates the drop should occur before the item.
     DROP_BEFORE,
 
     // Indicates the drop should occur after the item.
     DROP_AFTER,
 
     // Indicates the drop should occur on the item.
     DROP_ON
   };
 
+  virtual ~MenuDelegate();
+
   // Whether or not an item should be shown as checked. This is invoked for
   // radio buttons and check buttons.
   virtual bool IsItemChecked(int id) const;
 
   // The string shown for the menu item. This is only invoked when an item is
   // added with an empty label.
   virtual std::wstring GetLabel(int id) const;
 
   // The font for the menu item label.
   virtual const gfx::Font& GetLabelFont(int id) const;
@@ skipping 125 matching lines @@
   // Invoked prior to a menu being shown.
   virtual void WillShowMenu(MenuItemView* menu);
 
   // Invoked prior to a menu being hidden.
   virtual void WillHideMenu(MenuItemView* menu);
 };
 
 }  // namespace views
 
 #endif  // VIEWS_CONTROLS_MENU_MENU_DELEGATE_H_