LayoutTests/scrollingcoordinator/overflow-proxy-reattach.html - WebKit - Git at Google

 <!DOCTYPE html> <!-- webkit-test-runner [ AsyncOverflowScrollingEnabled=true AsyncFrameScrollingEnabled=true ] -->
 <iframe id=frame onload='test()' srcdoc='
 <style>
 .scroll { overflow:scroll; height:100px; border: 2px solid blue; }
 .content { position:relative; height: 1000px; }
 .abs { position:absolute; width:100px; height:100px; background-color:green; will-change:transform}
 </style>
 <div class=scroll id=scroller>
     <div class=content>
         <div class=abs></div>
     </div>
 </div>'></iframe>
 <script>
 async function test() {
     frame.contentDocument.querySelector('.scroll').scrollTop = 50;

     if (!window.testRunner)
         return;
     testRunner.waitUntilDone();

     await new Promise(requestAnimationFrame);

     internals.setPageIsInWindow(false);

     await new Promise(requestAnimationFrame);

     internals.setPageIsInWindow(true);

     await new Promise(requestAnimationFrame);

     testRunner.notifyDone();
 }
 </script>
	<!DOCTYPE html> <!-- webkit-test-runner [ AsyncOverflowScrollingEnabled=true AsyncFrameScrollingEnabled=true ] -->
	<iframe id=frame onload='test()' srcdoc='
	<style>
	.scroll { overflow:scroll; height:100px; border: 2px solid blue; }
	.content { position:relative; height: 1000px; }
	.abs { position:absolute; width:100px; height:100px; background-color:green; will-change:transform}
	</style>
	<div class=scroll id=scroller>
	<div class=content>
	<div class=abs></div>
	</div>
	</div>'></iframe>
	<script>
	async function test() {
	frame.contentDocument.querySelector('.scroll').scrollTop = 50;

	if (!window.testRunner)
	return;
	testRunner.waitUntilDone();

	await new Promise(requestAnimationFrame);

	internals.setPageIsInWindow(false);

	await new Promise(requestAnimationFrame);

	internals.setPageIsInWindow(true);

	await new Promise(requestAnimationFrame);

	testRunner.notifyDone();
	}
	</script>