chromium/chrome/test/data/devtools/oopif-input.html

<body>
  <script src="oopif-input.js"></script>
  <iframe style="width: 100px; height: 100px; position: absolute; top: 100px; left: 200px; border: 0;"></iframe>
  <script>
    var url = window.location.href;
    url = url.replace(/a\.com/, "b.com");
    url = url.replace(/oopif-input\.html/, "oopif-input-iframe.html");
    document.querySelector('iframe').setAttribute('src', url);
  </script>
</body>