chromium/chrome/test/data/chromedriver/cross_domain_iframe.html

<!DOCTYPE html>
<html>
  <head>
    <title>Contains a nested (hopefully OOPIF) iframe</title>
  </head>
  <body>
  <script>
document.body.onload = () => {
  let iframe = document.getElementsByTagName('iframe')[0];
  pathname = window.location.pathname.replace('cross_domain_iframe', 'outer');
  iframe.src = (window.location.protocol + '//' + 'localhost' +
      ':' + window.location.port + pathname);
}
  </script>
    <p><a href="#one">One</a></p>
    <iframe>
  </body>
</html>