chromium/third_party/blink/web_tests/external/wpt/xhr/resources/init.htm

<!doctype html>
<html>
  <head>
    <title>support init file</title>
  </head>
  <body>
    <script>
      onload = function() {
        // Run async, because navigations from inside onload can be a bit weird.
        setTimeout(function() {
          if (parent != window) {
            parent.init()
          } else {
            opener.init();
          }
        }, 0);
      }
    </script>
  </body>
</html>