<!DOCTYPE HTML> <html class="reftest-wait"> <head> <style type="text/css"> @keyframes anim { 0% { transform: translate(0px) } 100% { transform: translate(100px) } } div { width: 100px; height: 100px; background-color: white; } </style> </head> <body> <div></div> <script type="application/javascript"> window.addEventListener("load", function() { document.querySelector("div").setAttribute("style", "animation: 100s 300s anim linear"); advance_clock(200000); advance_clock(300000); Promise.resolve().then(function() { SpecialPowers.DOMWindowUtils.restoreNormalRefresh(); }).then(function() { document.documentElement.className = ""; }); }); function advance_clock(milliseconds) { SpecialPowers.DOMWindowUtils.advanceTimeAndRefresh(milliseconds); } </script> </html>