chromium/third_party/blink/web_tests/fast/loader/resources/subframe-with-unload-handler.html

<html>
<head>
<script>

window.onload = function() {
    alert("Subframe onload");
}

window.onunload = function() { 
    alert("Subframe onunload")
}

window.onpageshow = function(evt) {
    alert("Subframe onpageshow");
}

window.onpagehide = function(evt) {
    alert("Subframe onpagehide");
}

</script>
</head>
<body>
This subframe has an unload handler.
</body>
</html>