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

chrome/browser/ui/webui/chromeos/login/base_screen_handler_utils.h

 // Copyright (c) 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 CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_BASE_SCREEN_HANDLER_UTILS_H_
 #define CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_BASE_SCREEN_HANDLER_UTILS_H_
 
 #include <cstddef>
 #include <string>
 
 #include "base/callback.h"
 #include "base/logging.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "base/values.h"
 
 namespace chromeos {
 
 template<typename T>
 struct UnwrapConstRef {
   typedef T Type;
 };
 
 template<typename T>
@@ skipping 137 matching lines @@
       !GetArg(args, 3, &arg4)) {
     NOTREACHED();
     return;
   }
   callback.Run(arg1, arg2, arg3, arg4);
 }
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_BASE_SCREEN_HANDLER_UTILS_H_