Use a direct include of strings headers in chrome/test/.

chrome/test/webdriver/webdriver_session.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_TEST_WEBDRIVER_WEBDRIVER_SESSION_H_
 #define CHROME_TEST_WEBDRIVER_WEBDRIVER_SESSION_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/callback_forward.h"
 #include "base/files/file_path.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "base/threading/thread.h"
 #include "chrome/common/automation_constants.h"
 #include "chrome/test/automation/automation_json_requests.h"
 #include "chrome/test/webdriver/frame_path.h"
 #include "chrome/test/webdriver/webdriver_automation.h"
 #include "chrome/test/webdriver/webdriver_basic_types.h"
 #include "chrome/test/webdriver/webdriver_capabilities_parser.h"
 #include "chrome/test/webdriver/webdriver_element_id.h"
 #include "chrome/test/webdriver/webdriver_logging.h"
 
@@ skipping 467 matching lines @@
   // (e.g., 18.0.995.0 -> 995). Only valid after Chrome has started.
   // See http://dev.chromium.org/releases/version-numbers.
   int build_no_;
 
   DISALLOW_COPY_AND_ASSIGN(Session);
 };
 
 }  // namespace webdriver
 
 #endif  // CHROME_TEST_WEBDRIVER_WEBDRIVER_SESSION_H_