Cleanup: Remove vector::at() calls in SimpleMenuModel. Do CHECKs instead.

ui/base/models/simple_menu_model.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 UI_BASE_MODELS_SIMPLE_MENU_MODEL_H_
 #define UI_BASE_MODELS_SIMPLE_MENU_MODEL_H_
 #pragma once
 
 #include <vector>
 
@@ skipping 137 matching lines @@
   void set_delegate(Delegate* delegate) { delegate_ = delegate; }
   Delegate* delegate() { return delegate_; }
 
   MenuModelDelegate* menu_model_delegate() { return menu_model_delegate_; }
 
  private:
   struct Item;
 
   typedef std::vector<Item> ItemVector;
 
+  // Caller needs to call FlipIndex() if necessary. Returns |index|.
+  int ValidateItemIndex(int index) const;
+
   // Functions for inserting items into |items_|.
   void AppendItem(const Item& item);
   void InsertItemAtIndex(const Item& item, int index);
   void ValidateItem(const Item& item);
 
   // Notify the delegate that the menu is closed.
   void OnMenuClosed();
 
   ItemVector items_;
 
   Delegate* delegate_;
 
   MenuModelDelegate* menu_model_delegate_;
 
   base::WeakPtrFactory<SimpleMenuModel> method_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SimpleMenuModel);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_MODELS_SIMPLE_MENU_MODEL_H_