chromium/third_party/blink/web_tests/fast/dom/resources/cross-frame-node-prototype-iframe.html

<script type="text/javascript">

HTMLFormElement.prototype.bar = 'bar';

window.onload = function (e) {
    top.document.body.addEventListener('click', function (e) {
        var target = e.target;
    }, true);
    top.document.getElementsByTagName("input")[0].click();
}

</script>