sandbox-navigation-timing-iframe.tentative.html

<!DOCTYPE html>
<meta charset="utf-8">
<script>
  let result;
  try {
    parent.document.getElementsByClassName('script');
    result = 'iframe not sandboxed'
  } catch (e) {
    result = 'iframe sandboxed(' + e.message + ')';
  }
  window.onmessage = m => {
    window.parent.postMessage({
      result: result
    }, '*');
  };
</script>

chromium/third_party/blink/web_tests/external/wpt/html/browsers/sandboxing/sandbox-navigation-timing-iframe.tentative.html