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

chrome/browser/chromeos/login/oauth2_token_fetcher.cc

 // 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.
 
 #include "chrome/browser/chromeos/login/oauth2_token_fetcher.h"
 
 #include "base/logging.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "chrome/browser/chromeos/cros/cros_library.h"
 #include "chrome/browser/chromeos/net/connectivity_state_helper.h"
 #include "content/public/browser/browser_thread.h"
 #include "google_apis/gaia/gaia_constants.h"
 #include "google_apis/gaia/google_service_auth_error.h"
 
 using content::BrowserThread;
 
 namespace {
 
@@ skipping 95 matching lines @@
         base::TimeDelta::FromMilliseconds(kRequestRestartDelay));
     return;
   }
   LOG(ERROR) << "Unrecoverable error or retry count max reached. State: "
              << error.state() << ", network error: " << error.network_error()
              << ", message: " << error.error_message();
   error_handler.Run();
 }
 
 }  // namespace chromeos