Use a direct include of strings headers in x/.

chrome/browser/ui/views/keyboard_access_browsertest.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.
 
 // This functionality currently works on Windows and on Linux when
 // toolkit_views is defined (i.e. for Chrome OS). It's not needed
 // on the Mac, and it's not yet implemented on Linux.
 
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "base/time.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
 #include "chrome/browser/ui/views/toolbar_view.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/interactive_test_utils.h"
 #include "chrome/test/base/ui_test_utils.h"
@@ skipping 413 matching lines @@
       browser(), ui::VKEY_BROWSER_FORWARD, false, false, false, false));
 
   string16 after_forward;
   ASSERT_TRUE(ui_test_utils::GetCurrentTabTitle(browser(), &after_forward));
 
   EXPECT_EQ(before_back, after_forward);
 }
 #endif
 
 }  // namespace