Use a direct include of strings headers in chrome/browser/r*-s*/.

chrome/browser/signin/signin_names_io_thread.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 CHROME_BROWSER_SIGNIN_SIGNIN_NAMES_IO_THREAD_H_
 #define CHROME_BROWSER_SIGNIN_SIGNIN_NAMES_IO_THREAD_H_
 
 #include <set>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
 namespace content {
 class NotificationDetails;
 class NotificationSource;
 }
 
 
 // This class provides access to a list of email addresses for all profiles
@@ skipping 40 matching lines @@
   // Updates the email set on the I/O thread.  Protected for testing.
   void UpdateOnIOThread(int type, const string16& email);
 
   scoped_ptr<content::NotificationRegistrar> registrar_;
   EmailSet emails_;
 
   DISALLOW_COPY_AND_ASSIGN(SigninNamesOnIOThread);
 };
 
 #endif  // CHROME_BROWSER_SIGNIN_SIGNIN_NAMES_IO_THREAD_H_