chromium/third_party/blink/web_tests/compositing/overflow/overflow-positioning.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
   "http://www.w3.org/TR/html4/loose.dtd">

<html lang="en">
<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
  <title>25052 testcase</title>
  <style type="text/css" media="screen">
  body {
      margin: 100px;
  }
  
  #container {
    position: relative;
    overflow: hidden;
    height: 200px;
    width: 200px;
    border: 1px solid black;
    z-index: 0;
  }
  
  #header {
    position: relative;
    width: 100%;
    height: 100px;
    background-color: rgba(128, 128, 0, 0.2);
  }

  #hanger {
    position: absolute;
    left: -200px;
    height: 100px;
    width: 150px;
    background-color: blue;
  }
  
  #mover {
    position: absolute;
    top: 0;
    height: 150px;
    width: 150px;
    background-color: green;
    transition: transform 1000s;
  }
  
  #mover:hover {
    transform: translate(0px, 100px);
  }
  #mover.moving {
    transform: translate(0px, 100px);
  }
  </style>
  <script type="text/javascript" charset="utf-8">
    if (window.testRunner)
      testRunner.waitUntilDone();

    function waitForCompositor() {
      return document.body.animate({opacity: [1, 1]}, 1).finished;
    }

    function startTest()
    {
      var mover = document.getElementById('mover');
      getComputedStyle(mover).transform; // Force style recalc
      mover.className = 'moving';
      if (window.internals)
        internals.pauseAnimations(0);

      waitForCompositor().then(() => {
        if (window.testRunner) {
          testRunner.notifyDone();
        }
      });
    }

    window.addEventListener('load', startTest, false);
  </script>
</head>
<body>

<p>Things should not jump around when the green square starts the transition.</p>
<div id="container">
  <div id="header">
    <div id="hanger"></div>
  </div>
  <div id="mover">
  </div>
</div>

</body>
</html>