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

chrome/browser/chromeos/settings/device_settings_test_helper.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_CHROMEOS_SETTINGS_DEVICE_SETTINGS_TEST_HELPER_H_
 #define CHROME_BROWSER_CHROMEOS_SETTINGS_DEVICE_SETTINGS_TEST_HELPER_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "chrome/browser/chromeos/policy/device_policy_builder.h"
 #include "chrome/browser/chromeos/settings/device_settings_service.h"
 #include "chrome/browser/chromeos/settings/device_settings_test_helper.h"
 #include "chrome/browser/chromeos/settings/mock_owner_key_util.h"
 #include "chromeos/dbus/session_manager_client.h"
 #include "content/public/test/test_browser_thread.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace chromeos {
 
@@ skipping 149 matching lines @@
   // with the global instance (DeviceSettingsService::Get()).
   DeviceSettingsService device_settings_service_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DeviceSettingsTestBase);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_SETTINGS_DEVICE_SETTINGS_TEST_HELPER_H_