feature-policy/resources/nested-sandbox.html - external/github.com/web-platform-tests/wpt - Git at Google

 <!DOCTYPE html>
 <title>Return fullscreen feature policy state</title>
 <script>
   "use strict";
   window.onload = () => {
     window.parent.postMessage(document.featurePolicy.allowedFeatures().includes("fullscreen"),"*");
   };
 </script>
	<!DOCTYPE html>
	<title>Return fullscreen feature policy state</title>
	<script>
	"use strict";
	window.onload = () => {
	window.parent.postMessage(document.featurePolicy.allowedFeatures().includes("fullscreen"),"*");
	};
	</script>