servo/tests/wpt/web-platform-tests/resource-timing/resources/iframe-reload-TAO.sub.html

<style>
@font-face {
    font-family: ahem;
    src: url(http://{{domains[www]}}:{{ports[http][1]}}/resource-timing/resources/cors-ahem.py);
}
</style>
<div style="font-family: ahem;">This fetches ahem font.</div>
<script>
  if (location.hash === '#check') {
      document.fonts.ready.then(()=> {
        const entries = performance.getEntriesByName('http://{{domains[www]}}:{{ports[http][1]}}/resource-timing/resources/cors-ahem.py');
        if (entries.length != 1)
          return;
        const entry = entries[0];
        window.parent.postMessage({
            "domainLookupStart": entry.domainLookupStart,
            "domainLookupEnd": entry.domainLookupEnd,
            "connectStart": entry.connectStart,
            "connectEnd": entry.connectEnd
          }, "*");
      });
  } else {
      document.fonts.ready.then(() => {
        location.hash = 'check';
        location.reload();
      });
  }
</script>