chromium/third_party/blink/web_tests/fast/loader/resources/unload-hyperlink-targeted-subframe.html

<script>
addEventListener("unload", function() {
  var anc = document.getElementById("lk");
  var evt = document.createEvent("MouseEvents");
  evt.initMouseEvent(
      "click", true, true, window, 1, 0, 0, 0, 0,
      false, false, false, false, 0, anc);
  anc.dispatchEvent(evt);
}, false);
</script>
<a id="lk" target="_top"
   href="pass-and-notify-done.html">Link to iframe.</a>
<script>
window.onload = function() {
window.location = "about:blank";
}
</script>