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

chrome/test/base/web_ui_browsertest.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_BASE_WEB_UI_BROWSERTEST_H_
 #define CHROME_TEST_BASE_WEB_UI_BROWSERTEST_H_
 
 #include <string>
 #include <vector>
 
 #include "base/files/file_path.h"
 #include "base/memory/scoped_vector.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "content/public/test/js_injection_ready_observer.h"
 
 namespace base {
 class Value;
 }
 
 namespace content {
 class RenderViewHost;
 class WebUI;
@@ skipping 167 matching lines @@
   std::string preload_test_name_;
 
   // When this is non-NULL, this is The WebUI instance used for testing.
   // Otherwise the selected tab's web_ui is used.
   content::WebUI* override_selected_web_ui_;
 
   scoped_ptr<TestChromeWebUIControllerFactory> test_factory_;
 };
 
 #endif  // CHROME_TEST_BASE_WEB_UI_BROWSERTEST_H_