<!DOCTYPE html>
<title>
  Current animations should effectively apply will-change (i.e. force a
  stacking context) (ref)
</title>
<link rel="help" href="https://drafts.csswg.org/web-animations-1/#side-effects-section">
<link rel="author" href="mailto:bokan@chromium.org">
<style>
  .testcase {
    position: relative;
    margin: 2px;
    border: 1px solid black;
    width: 250px;
    height: 25px;
  }
  .label {
    flex-grow: 1;
  }
  .container {
    background-color: lightgrey;
    margin: 4px;
    displ