chromium/chrome/test/data/reduce_accept_language/same_origin_fenced_frame.html

<!DOCTYPE html>
<html>
<body>
    <fencedframe></fencedframe>
    <script>
        const url = new URL("subframe_simple.html", location.href);
        document.querySelector("fencedframe").config =
            new FencedFrameConfig(url);
    </script>
</body>
</html>