postMessage/resources/first-party-to-third-party-iframe.html - external/w3c/web-platform-tests - Git at Google

 <!doctype html>
 <meta charset=utf-8>
 <body>
 <script>
 // Step 3
 window.top.opener.postMessage("Site 1 Frame", window.top.opener.origin);
 </script>
 </body>
	<!doctype html>
	<meta charset=utf-8>
	<body>
	<script>
	// Step 3
	window.top.opener.postMessage("Site 1 Frame", window.top.opener.origin);
	</script>
	</body>