chromium/third_party/blink/web_tests/external/wpt/css/css-masking/clip-path/animations/clip-path-transition.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-transition-ref.html">
<style>
  .container {
    width: 100px;
    height: 100px;
    clip-path: circle(50% at 50% 50%);
    background-color: green;
    transition-property: clip-path;
    transition-duration: 20s;
    transition-timing-function: steps(2, jump-end);
    transition-delay: -9.999s;
  }
</style>
<script src="/common/reftest-wait.js"></script>
<script src="../../../../web-animations/resources/timing-utils.js"></script>

<body>
  <div class="container" id="target"></div>

  <script>
    function update() {
      document.getElementById('target').style.clipPath = "circle(30% at 30% 30%)";
      waitForAnimationTime(document.getAnimations()[0], 1).then(takeScreenshot);
    }
    requestAnimationFrame(function () {
      requestAnimationFrame(update);
    });
  </script>
</body>

</html>