chromium/third_party/blink/web_tests/svg/animations/updated-values-after-sandwich-order-change.html

<!DOCTYPE html>
<title>Updating the 'values' attribute after sandwich order change</title>
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<svg>
  <rect width="100" height="100">
    <animate attributeName="opacity" begin="0ms; 40ms; 70ms" dur="10ms" id="first" fill="freeze"/>
    <animate attributeName="opacity" begin="20ms; 50ms" dur="10ms" from="1" to="1" fill="freeze"/>
  </rect>
</svg>
<script>
  async_test(t => {
    let first_animate = document.getElementById("first");
    window.onload = t.step_func(() => {
      let svg = first_animate.ownerSVGElement;
      svg.pauseAnimations();
      window.requestAnimationFrame(t.step_func_done(() => {
        svg.unpauseAnimations();
        first_animate.setAttribute("values", "0; 1");
      }));
    });
  });
</script>