Add MenuModelAdapter to wrap ui::MenuModel with views::MenuDelegate interface.

ui/base/models/menu_model.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 UI_BASE_MODELS_MENU_MODEL_H_
 #define UI_BASE_MODELS_MENU_MODEL_H_
 #pragma once
 
 #include "base/memory/scoped_ptr.h"
 #include "base/string16.h"
@@ skipping 26 matching lines @@
 
   virtual ~MenuModel() {}
 
   // Returns true if any of the items within the model have icons. Not all
   // platforms support icons in menus natively and so this is a hint for
   // triggering a custom rendering mode.
   virtual bool HasIcons() const = 0;
 
   // Returns the index of the first item. This is 0 for most menus except the
   // system menu on Windows. |native_menu| is the menu to locate the start index
-  // within. It is guaranteed to be reset to a clean default state.
+  // within. It is guaranteed to be reset to a clean default state.  Some
+  // callers of this method may pass NULL for native_menu.
   // IMPORTANT: If the model implementation returns something _other_ than 0
   //            here, it must offset the values for |index| it passes to the
   //            methods below by this number - this is NOT done automatically!
   virtual int GetFirstItemIndex(gfx::NativeMenu native_menu) const;
 
   // Returns the number of items in the menu.
   virtual int GetItemCount() const = 0;
 
   // Returns the type of item at the specified index.
   virtual ItemType GetTypeAt(int index) const = 0;
@@ skipping 65 matching lines @@
   // Retrieves the model and index that contains a specific command id. Returns
   // true if an item with the specified command id is found. |model| is inout,
   // and specifies the model to start searching from.
   static bool GetModelAndIndexForCommandId(int command_id, MenuModel** model,
                                            int* index);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_MODELS_MENU_MODEL_H_