Use a direct include of strings headers in url/, win8/.

win8/test/open_with_dialog_async.h

 // Copyright (c) 2013 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 WIN8_TEST_OPEN_WITH_DIALOG_ASYNC_H_
 #define WIN8_TEST_OPEN_WITH_DIALOG_ASYNC_H_
 
 #include <windows.h>
 
 #include "base/callback_forward.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 
 namespace win8 {
 
 // Expected HRESULTS:
 //   S_OK - A choice was made.
 //   HRESULT_FROM_WIN32(ERROR_CANCELLED) - The dialog was dismissed.
 //   HRESULT_FROM_WIN32(RPC_S_CALL_FAILED) - OpenWith.exe died.
 typedef base::Callback<void(HRESULT)> OpenWithDialogCallback;
 
 // Calls SHOpenWithDialog on a dedicated thread, returning the result to the
 // caller via |callback| on the current thread.  The Windows SHOpenWithDialog
 // function blocks until the user makes a choice or dismisses the dialog (there
 // is no natural timeout nor a means by which it can be cancelled).  Note that
 // the dedicated thread will be leaked if the calling thread's message loop goes
 // away before the interaction completes.
 void OpenWithDialogAsync(HWND parent_window,
                          const string16& file_name,
                          const string16& file_type_class,
                          int open_as_info_flags,
                          const OpenWithDialogCallback& callback);
 
 }  // namespace win8
 
 #endif  // WIN8_TEST_OPEN_WITH_DIALOG_ASYNC_H_