chromium/third_party/blink/web_tests/http/tests/serviceworker/resources/insecure-parent.html

<!DOCTYPE html>
<meta charset="utf-8">
<script src="/resources/get-host-info.js?pipe=sub"></script>
<title>Page Title</title>
<body></body>
<script>
var iframe = document.createElement('iframe');
iframe.src = get_host_info().HTTP_ORIGIN +
    '/serviceworker/resources/insecure-inscope.html';
document.body.appendChild(iframe);

// The top frame messages us to message the subframe.
window.addEventListener('message', e => {
    iframe.contentWindow.postMessage(e.data, '*');
  });
</script>