Use a direct include of strings headers in chrome/browser/ui/cocoa/.

chrome/browser/ui/cocoa/bookmarks/bookmark_drag_drop_cocoa.mm

 // Copyright 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.
 
 #include "chrome/browser/ui/cocoa/bookmarks/bookmark_drag_drop_cocoa.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include <cmath>
 
 #include "base/logging.h"
 #include "base/memory/scoped_nsobject.h"
 #include "base/message_loop.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "base/strings/sys_string_conversions.h"
 #include "chrome/browser/bookmarks/bookmark_model.h"
 #include "chrome/browser/bookmarks/bookmark_model_factory.h"
 #include "chrome/browser/bookmarks/bookmark_node_data.h"
 #include "chrome/browser/bookmarks/bookmark_pasteboard_helper_mac.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/bookmarks/bookmark_drag_drop.h"
 #import "chrome/browser/ui/cocoa/bookmarks/bookmark_bar_controller.h"
 #include "grit/ui_resources.h"
 #include "ui/base/resource/resource_bundle.h"
@@ skipping 151 matching lines @@
              offset:NSZeroSize
               event:drag_event
          pasteboard:[NSPasteboard pasteboardWithName:NSDragPboard]
              source:nil
           slideBack:YES];
 
   base::MessageLoop::current()->SetNestableTasksAllowed(was_nested);
 }
 
 }  // namespace chrome