chromium/chrome/test/data/extensions/perf_tests/many_frames.html

<!DOCTYPE html>
<body>
<script>
function runTest(callback) {
  const start = performance.now();
  const frameCount = 100;
  let framesLoaded = 0;
  function onFrameLoad() {
    if (++framesLoaded == frameCount)
      callback(performance.now() - start);
  }

  const body = document.body;
  for (let i = 0; i < frameCount; i++) {
    const iframe = document.createElement('iframe');
    iframe.src = '/title1.html';
    iframe.onload = onFrameLoad;
    body.appendChild(iframe);
  }
}
</script>
</body>