<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Animating pseduo-element on scroller</title>
</head>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/web-animations/testcommon.js"></script>
<script src="./support/testcommon.js"></script>
<script src="testcommon.js"></script>
<style type="text/css">
.scroller {
  overflow: scroll;
  width: 100px;
  heig