<html>
<head>
<title>PostMessage Test</title>
<script>
var messagesReceived = 0;
window.addEventListener("message", messageReceived, false);
function messageReceived(event) {
  messagesReceived++;
  document.body.appendChild(document.createTextNode('Message ' + messagesReceived + '.'));
}
</script>
</head>
<body>
Test page.
</body>
</html>