Use a direct include of strings headers in ui/, part 2.

ui/base/models/button_menu_item_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_BUTTON_MENU_ITEM_MODEL_H_
 #define UI_BASE_MODELS_BUTTON_MENU_ITEM_MODEL_H_
 
 #include <vector>
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "ui/base/ui_export.h"
 
 namespace ui {
 
 // A model representing the rows of buttons that should be inserted in a button
 // containing menu item.
 class UI_EXPORT ButtonMenuItemModel {
  public:
   // Types of buttons.
   enum ButtonType {
@@ skipping 83 matching lines @@
   std::vector<Item> items_;
 
   Delegate* delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(ButtonMenuItemModel);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_MODELS_BUTTON_MENU_ITEM_MODEL_H_