chromium/third_party/blink/web_tests/external/wpt/css/css-contain/contain-animation-001.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Containment Test: contain is not animatable</title>
<link rel="author" title="Florian Rivoal" href="https://florian.rivoal.net/">
<link rel="help" href="https://drafts.csswg.org/css-contain/#contain-property">
<link rel="match" href="../reference/ref-filled-green-100px-square.xht">
<meta name=assert content="the contain property is not animatable">
<style>
div {
  border: 50px solid green;
  background: red;
  position: absolute; /* for shrinkwrap */
  contain: strict;

  animation-duration: 1s;
  animation-name: bad;
  animation-play-state: paused;

  font-size: 100px;
}

@keyframes bad {
  from {
    contain: none;
  }
}
</style>

<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
<div>&nbsp;</div>