chrome/test/data/fast_shutdown/on_unloader.html

<script>
addEventListener("unload", function() {
  var expires = new Date();
  expires.setMinutes(expires.getMinutes() + 1);
  document.cookie = "unloaded=ohyeah;path=/;expires=" + expires.toUTCString();
}, false);
open('on_before_unloader.html');
</script>