chromium/third_party/blink/web_tests/compositing/overflow/resources/composited-subframe.html

<!DOCTYPE html>

<html>
<head>
  <style type="text/css" media="screen">
    body { background-color:silver }
    
    .box {
        height: 200px;
        width: 200px;
        margin: 10px;
        padding: 5px;
        background-color: blue;
        will-change: transform;
        overflow:hidden;
    }
    .box:hover {
        transform: none;
    }
  </style>
</head>
<body>

    <div id="iframe-content" class="box">
    </div>

</body>
</html>