chromium/third_party/blink/web_tests/external/wpt/css/css-masking/clip-path/animations/clip-path-animation.html

<!DOCTYPE html>
<html class="reftest-wait">
<link rel="help" href="https://drafts.csswg.org/css-shapes-1/#basic-shape-interpolation">
<link rel="match" href="clip-path-animation-ref.html">
<style>
.container {
  width: 100px;
  height: 100px;
  background-color: green;
  animation: clippath 20s steps(2, jump-end) -9.999s;
}
@keyframes clippath {
  0%   { clip-path: circle(50% at 50% 50%); }
  100% { clip-path: circle(20% at 20% 20%); }
}
</style>
<script src="/common/reftest-wait.js"></script>
<script src="../../../../web-animations/resources/timing-utils.js"></script>
<body>
<div class="container"></div>

<script>
  waitForAnimationTime(document.getAnimations()[0], 1).then(takeScreenshot);
</script>
</body>
</html>