disable_web_security_cross_origin.html

<!DOCTYPE html>
<body>
<script>
var iframe = document.createElement('iframe');
iframe.onload = (_ => {
    document.title = "LOADED";
  });
iframe.src = location.search.substring(1);
document.body.appendChild(iframe);
</script>
</body>

chromium/content/test/data/service_worker/disable_web_security_cross_origin.html