chromium/chrome/test/data/extensions/declarative_net_request/post_to_page_with_two_frames.html

<html>
  <body>
    <form id="form" method="POST" action="./page_with_two_frames.html"></form>

    <script type="text/javascript">
      document.getElementById("form").submit();
    </script>
  </body>
</html>