third_party/blink/web_tests/paint/invalidation/details-open-repaint.html - chromium/src - Git at Google

 <!DOCTYPE html>

 <script src="resources/text-based-repaint.js"></script>
 <script>
 window.onload = runRepaintAndPixelTest;

 function repaintTest() {
   document.getElementsByTagName('details')[0].setAttribute('open', true);
 }
 </script>

 <p>This test passes if the arrow rotates to the open position.</p>
 <details>
   <input>
   <summary>summary</summary>
 </details>
	<!DOCTYPE html>

	<script src="resources/text-based-repaint.js"></script>
	<script>
	window.onload = runRepaintAndPixelTest;

	function repaintTest() {
	document.getElementsByTagName('details')[0].setAttribute('open', true);
	}
	</script>

	<p>This test passes if the arrow rotates to the open position.</p>
	<details>
	<input>
	<summary>summary</summary>
	</details>