streams/transferable/resources/echo-iframe.html - external/github.com/web-platform-tests/wpt - Git at Google

 <!DOCTYPE html>
 <meta charset="utf-8">
 <script>
 addEventListener('message', evt => {
   evt.source.postMessage(evt.data, '*', [evt.data]);
 });
 </script>
	<!DOCTYPE html>
	<meta charset="utf-8">
	<script>
	addEventListener('message', evt => {
	evt.source.postMessage(evt.data, '*', [evt.data]);
	});
	</script>