chromium/third_party/blink/web_tests/external/wpt/css/css-transforms/animation/rotate-transform-equivalent-ref.html

<!doctype html>
<html class="reftest-wait">
<meta charset="utf-8">
<title>Reference for rotate transform equivalent</title>
<script src="/common/reftest-wait.js"></script>
<style>
  .block {
    border: 2px solid white; /* Avoid anti-aliasing artifacts */
    height: 100px;
    width: 100px;
    position: absolute;
    left: 100px;
    top: 100px;
  }

  .overlay {
    background: green;
    z-index: 2;
  }
</style>
<body>
  <div id="transform" class="block overlay"></div>

<script>
  'use strict';

  async function waitForNextFrame() {
    return new Promise(resolve => {
      window.requestAnimationFrame(() => {
        resolve();
      });
    });
  }

  async function createAnimation(elementName, keyframes) {
    const element = document.getElementById(elementName);
    const anim = element.animate(keyframes, 1000);
    anim.pause();
    anim.currentTime = 500;
    return anim.ready;
  }

  onload = async function() {
    await waitForNextFrame();

    await createAnimation('transform', [
        {transform: 'matrix3d(1, 0, 0, 0,   0, 0, 1, 0,   0, -1, 0, 0,   0, 0, 0, 1)'},
        {transform: 'matrix(0, 1, -1, 0, 0, 0)'}]);

    await waitForNextFrame();
    takeScreenshot();
  };
</script>
</body>