chromium/third_party/blink/web_tests/external/wpt/fenced-frame/resources/download-inner.html

<!DOCTYPE html>
<html>

<head>
  <title>The page triggering download embedded as a Fenced Frame</title>
  <script src="/resources/testdriver.js"></script>
  <script src="/resources/testdriver-vendor.js"></script>
  <script src="download-helper.js"></script>
  <script src="utils.js"></script>
  <script>
    window.addEventListener('DOMContentLoaded', async () => {
      const [download_key, download_ack_key] = parseKeylist();
      const type = new URL(location).searchParams.get('type');
      const href = `download-stash.py?token=${download_key}`;

      if (type == 'anchor') {
        const anchor = document.querySelector('#download');
        anchor.href = href;
        test_driver.click(anchor);
      } else {
        const delay = StreamDownloadFinishDelay();
        location.href = `${href}&finish-delay=${delay}`
      }

      await writeValueToServer(download_ack_key, 'Triggered the action for download');
    });
  </script>
</head>

<body>
  <a id="download" download>Download</a>
</body>

</html>