<!DOCTYPE html>
<html>
<head>
    <style>
        body {
            height: 1000px;
        }
        .clipper {
            margin: 20px;
            padding: 10px;
            width: 300px;
            height: 100px;
            overflow: hidden;
            background-color: gray;
        }
        .changed .clipper {
            height: 300px;
        }
        .content {
            transform: translateZ(0);
            background-color: green;
            height: 300px;
        }
    </style>
    <script>
        if (window.testRunner)
            testRunner.waitUntilDone();

        window.addEventListener('load', () => {
            requestAnimationFrame(() => {
                document.body.classList.add('changed');

                if (window.testRunner)
                    testRunner.notifyDone();
            });
        }, false);
    </script>
</head>
<body>
    <div class="clipper">
        <div class="content">
            &nbsp;
        </div>
    </div>
</body>
</html>