ManualTests/compositing/fixed-position-out-of-view-scroll-prepaint.html - WebKit - Git at Google

 <!DOCTYPE html>
 <html>
 <head>
   <style>
     body {
       height: 2000px;
       margin: 0px;
       padding: 0px;
     }
     .main {
       position: fixed;
     }
     .fixed {
       position: fixed;
       width: 100%;
       height: 100px;
       left: 0px;
       bottom: -100px;
       background-color: red;
     }
   </style>
 </head>

 <body>
   <div class="main">
     This test is applicable on platforms that do accelerated compositing, can prepaint out-of-view contents and can scroll the contents into the viewport without repainting them.<p>
     The following settings need to be enabled:<p>
     - acceleratedCompositingForFixedPositionEnabled<br>
     - fixedPositionCreatesStackingContext<p>
     To test, scroll the page up and down. The test passes if there is no temporary or permanent red in the page.
   </div>

   <!-- An out-of-view fixed element that should be never visible -->
   <div class="fixed"></div>
 </body>
 </html>
	<!DOCTYPE html>
	<html>
	<head>
	<style>
	body {
	height: 2000px;
	margin: 0px;
	padding: 0px;
	}
	.main {
	position: fixed;
	}
	.fixed {
	position: fixed;
	width: 100%;
	height: 100px;
	left: 0px;
	bottom: -100px;
	background-color: red;
	}
	</style>
	</head>

	<body>
	<div class="main">
	This test is applicable on platforms that do accelerated compositing, can prepaint out-of-view contents and can scroll the contents into the viewport without repainting them.<p>
	The following settings need to be enabled:<p>
	- acceleratedCompositingForFixedPositionEnabled<br>
	- fixedPositionCreatesStackingContext<p>
	To test, scroll the page up and down. The test passes if there is no temporary or permanent red in the page.
	</div>

	<!-- An out-of-view fixed element that should be never visible -->
	<div class="fixed"></div>
	</body>
	</html>