src/third_party/web_platform_tests/intersection-observer/resources/nested-cross-origin-grand-child-iframe.html - cobalt - Git at Google

 <!DOCTYPE html>
 <div id="target" style="height: 100px; background-color: green;"></div>
 <script>
 const observer = new IntersectionObserver(records => {
   records.forEach(record => {
     if (record.isIntersecting) {
       window.top.postMessage(record.isIntersecting, "*");
     }
   });
 }, {});
 observer.observe(target);
 window.addEventListener("load", () => {
   window.top.postMessage("ready", "*");
 });
 </script>
	<!DOCTYPE html>
	<div id="target" style="height: 100px; background-color: green;"></div>
	<script>
	const observer = new IntersectionObserver(records => {
	records.forEach(record => {
	if (record.isIntersecting) {
	window.top.postMessage(record.isIntersecting, "*");
	}
	});
	}, {});
	observer.observe(target);
	window.addEventListener("load", () => {
	window.top.postMessage("ready", "*");
	});
	</script>