chrome/test/data/perf/tab-spinner-case.html - chromium/src - Git at Google

 <body>
   <div>This document is going to take a long time to load.</div>
 <script>
   const now = new Date();
   const seconds = 1000;
   while ((new Date() - now) < 10 * seconds) {};
 </script>
	<body>
	<div>This document is going to take a long time to load.</div>
	<script>
	const now = new Date();
	const seconds = 1000;
	while ((new Date() - now) < 10 * seconds) {};
	</script>