chromium/src/third_party/blink/web_tests/http/tests/wasm/resources/remote_frame.html - manifest_repos/chromium_src - Git at Google

 <!DOCTYPE html>
 <script>
 function listener(event) {
   var ret = event.data;
   if (!ret) ret = "didn't make it"
   event.source.postMessage(ret, event.origin);
 }

 addEventListener("message", listener, false);

 </script>
	<!DOCTYPE html>
	<script>
	function listener(event) {
	var ret = event.data;
	if (!ret) ret = "didn't make it"
	event.source.postMessage(ret, event.origin);
	}

	addEventListener("message", listener, false);

	</script>