Replace ButtonDropDown menu implementation (Menu2) with MenuItemView.

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 170 matching lines @@
                                        const gfx::Point& screen_point,
                                        MenuItemView::AnchorPosition* anchor,
                                        bool* has_mnemonics,
                                        MenuButton** button);
 
   // Returns the max width menus can grow to be.
   virtual int GetMaxWidthForMenu(MenuItemView* menu);
 
   // 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_