unload-bubbles.html

Enable keyboard shortcuts

<!doctype html>

<html>

<head><title>Document</title></head>

<body>

<h1>Document</h1>

<script>

window.addEventListener("load", function() {

  window.addEventListener("visibilitychange", event => {

    opener.postMessage({

                        target: event.target.nodeName,

                        state: document.visibilityState,

                        bubbles: event.bubbles

                      }, "*");

});

  opener.postMessage("close", "*");

});

</script>

</body>

</html>