Use a direct include of strings headers in extensions/, google_apis/, gpu/.

google_apis/gaia/gaia_auth_fetcher.cc

 // 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.
 
 #include "google_apis/gaia/gaia_auth_fetcher.h"
 
 #include <algorithm>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
-#include "base/string_util.h"
-#include "base/stringprintf.h"
 #include "base/strings/string_split.h"
+#include "base/strings/string_util.h"
+#include "base/strings/stringprintf.h"
 #include "base/values.h"
 #include "google_apis/gaia/gaia_auth_consumer.h"
 #include "google_apis/gaia/gaia_constants.h"
 #include "google_apis/gaia/gaia_urls.h"
 #include "google_apis/gaia/google_service_auth_error.h"
 #include "net/base/escape.h"
 #include "net/base/load_flags.h"
 #include "net/http/http_response_headers.h"
 #include "net/http/http_status_code.h"
 #include "net/url_request/url_fetcher.h"
@@ skipping 912 matching lines @@
     NOTREACHED();
   }
 }
 
 // static
 bool GaiaAuthFetcher::IsSecondFactorSuccess(
     const std::string& alleged_error) {
   return alleged_error.find(kSecondFactor) !=
       std::string::npos;
 }