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

chrome/browser/chromeos/login/oauth2_login_verifier.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_login_verifier.h"
 
 #include <vector>
 
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
-#include "base/string_util.h"
-#include "base/stringprintf.h"
+#include "base/strings/string_util.h"
+#include "base/strings/stringprintf.h"
 #include "base/time.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/gaia_urls.h"
 
 using content::BrowserThread;
 
 namespace {
@@ skipping 191 matching lines @@
   LOG(ERROR) << "Unrecoverable error or retry count max reached for "
              << operation_id;
   UMA_HISTOGRAM_ENUMERATION(
       base::StringPrintf("OAuth2Login.%sFailure", operation_id),
       error.state(),
       GoogleServiceAuthError::NUM_STATES);
   error_handler.Run();
 }
 
 }  // namespace chromeos