third_party/blink/web_tests/resources/window-postmessage-open-close.html - chromium/src - Git at Google

 <!DOCTYPE html>
 <!-- Used when testing access of a closed/detached window's properties -->
 <html>
 <body onunload="opener.postMessage('closed', '*');">
 <script>
 opener.postMessage("opened", "*");
 </script>
 </body>
 </html>
	<!DOCTYPE html>
	<!-- Used when testing access of a closed/detached window's properties -->
	<html>
	<body onunload="opener.postMessage('closed', '*');">
	<script>
	opener.postMessage("opened", "*");
	</script>
	</body>
	</html>