<!DOCTYPE html>
<html>
<head>
<script>
// HACK: This is not an ideal way to deliver chrome messages
// to an inner frame content but seems only way that would
// make `event.source` this (outer frame) window.
window.onmessage = function(event) {
var frame = document.querySelector("iframe");
var content = frame.contentWindow;
// If message is posted from chrome it has no `event.source`.
if (event.source === null)
content.postMessage(event.data, "*");
};
</script>
</head>
<body style="overflow: hidden"></body>
</html>