shell.html

<!doctype html>
<html>
<head>
    <meta charset="utf-8" />
    <link rel="stylesheet" type="text/css" href="shell.css">
    <title>event-loop test</title>
</head>
<body>
<button id="testiframeButton" onclick="startTestInIFrame()" style="font-size:xx-large">Start test in iFrame</button>
<script>
'use strict';


function startTestInIFrame() {
    var iframes = document.querySelectorAll('iframe');
    for (var i=0; i<iframes.length; i++)
        iframes[i].parentNode.removeChild(iframes[i]);
    var iframe = document.createElement('iframe');
    iframe.setAttribute('src', 'test.html');
    iframe.width = '300px';
    iframe.height = '300px';
    document.body.appendChild(iframe);

    window.setTimeout(function(ev) {
        iframe.contentWindow.postMessage('startTest', '*');
    }, 300);
}

</script>
</body>
</html>