chromium/third_party/blink/web_tests/http/tests/priorities/resources/iframe.html

<script src="common.js"></script>
<script>
  observeAndReportResourceLoadPriority(new URL('../../resources/dummy.html?iframe', location));
</script>

<iframe src="../../resources/dummy.html?iframe" onload="reportLoaded()" onerror="rejector()"></iframe>