chromium/chrome/test/data/download-anchor-attrib.html

<html>
<head><title>Download Test for &lt;a download&gt;</title></head>
<body>
<a id='red-dot' href="anchor_download_test.png" download='a_red_dot.png'>Download Red Dot!</a>
<script>
window.setTimeout(function() {
  var evt = document.createEvent("MouseEvent");
  evt.initMouseEvent('click', true, true);
  document.getElementById('red-dot').dispatchEvent(evt);
}, 0);
</script>
</body>
</html>