chromium/src/third_party/blink/web_tests/external/wpt/html/browsers/windows/nested-browsing-contexts/resources/frameElement-sibling-accessed.html - manifest_repos/chromium_src - Git at Google

 <!DOCTYPE html>
 <meta charset="utf-8">
 <title>This page will set its document.domain on request so that its sibling can access it</title>

 <h1>I did get loaded</h1>

 <script>
 "use strict";

 window.onmessage = e => {
   const { newDocumentDomain } = e.data;
   document.domain = newDocumentDomain;

   parent.postMessage("done", "*");
 };
 </script>
	<!DOCTYPE html>
	<meta charset="utf-8">
	<title>This page will set its document.domain on request so that its sibling can access it</title>

	<h1>I did get loaded</h1>

	<script>
	"use strict";

	window.onmessage = e => {
	const { newDocumentDomain } = e.data;
	document.domain = newDocumentDomain;

	parent.postMessage("done", "*");
	};
	</script>