sandbox-mandatory-flags-iframe.sub.html

<!DOCTYPE html>
<title>Iframe content to load a fenced frame and report a value to the server</title>
<script src="utils.js"></script>

<body>
<script>
  const fencedframe = document.createElement("fencedframe");
  fencedframe.config = new FencedFrameConfig(
      generateURL("sandbox-mandatory-flags-inner.sub.html?key={{GET[key]}}" +
          "&value={{GET[value]}}", []));
  document.body.appendChild(fencedframe);
</script>
</body>

chromium/third_party/blink/web_tests/external/wpt/fenced-frame/resources/sandbox-mandatory-flags-iframe.sub.html