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

chrome/test/webdriver/webdriver_key_converter_unittest.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 <string>
 #include <vector>
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/test/automation/automation_json_requests.h"
 #include "chrome/test/webdriver/webdriver_key_converter.h"
 #include "chrome/test/webdriver/webdriver_test_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace webdriver {
 
 void CheckEvents(const string16& keys,
                  WebKeyEvent expected_events[],
@@ skipping 348 matching lines @@
       CreateKeyUpEvent(ui::VKEY_CONTROL, 0)};
   string16 keys;
   keys.push_back(static_cast<char16>(0xE008U));
   keys.push_back(static_cast<char16>(0xE009U));
 
   CheckEvents(keys, event_array, true /* release_modifiers */,
       arraysize(event_array), 0);
 }
 
 }  // namespace webdriver