chromium/chrome/test/data/password/frame_detached_after_submit.html

<html>
  <body>
    <iframe src="frame_detached_after_submit_iframe_form.html" title="Reset password" id="password_reset_iframe" name="password_reset_iframepassword_reset_iframe">
    </iframe>
    <script type="text/javascript">
      window.addEventListener("message", (event) => {
        var iframe = document.getElementById('password_reset_iframe');
        iframe.parentNode.removeChild(iframe);
      });
    </script>
  </body>
</html>