Use a direct include of strings headers in ui/, part 1.

ui/base/cocoa/menu_controller.h

 // Copyright 2013 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_COCOA_MENU_CONTROLLER_H_
 #define UI_BASE_COCOA_MENU_CONTROLLER_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/memory/scoped_nsobject.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "ui/base/ui_export.h"
 
 namespace ui {
 class MenuModel;
 }
 
 // A controller for the cross-platform menu model. The menu that's created
 // has the tag and represented object set for each menu item. The object is a
 // NSValue holding a pointer to the model for that level of the menu (to
 // allow for hierarchical menus). The tag is the index into that model for
@@ skipping 57 matching lines @@
               atIndex:(NSInteger)index
             fromModel:(ui::MenuModel*)model;
 - (NSMenu*)menuFromModel:(ui::MenuModel*)model;
 // Returns the maximum width for the menu item. Returns -1 to indicate
 // that there's no maximum width.
 - (int)maxWidthForMenuModel:(ui::MenuModel*)model
                  modelIndex:(int)modelIndex;
 @end
 
 #endif  // UI_BASE_COCOA_MENU_CONTROLLER_H_