<!DOCTYPE html>
<html>
<head>
    <style>
        .container {
            position: relative;
            margin: 20px;
        }
        .box {
            position: absolute;
            top: 0;
            left: 0;
            width: 200px;
            height: 200px;
            background-color: silver;
        }
        .composited {
            transform: translateZ(1px);
        }
        .sibling {
            top: 300px;
            background-color: gray;
        }
        .negative {
            z-index: -1;
            background-color: red;
        }
        .positive {
            z-index: 1;
            background-color: green;
        }
    </style>
    <script>
        if (window.testRunner)
            testRunner.waitUntilDone();

        window.addEventListener('load', () => {
            setTimeout(() => {
                document.getElementById('target').classList.add('composited');
                if (window.testRunner)
                    testRunner.notifyDone();
            }, 0);
        }, false);
    </script>
</head>
<body>
    <div class="container">
        <div class="composited child box">
            <div class="negative box">&nbsp;</div>
            <div class="composited positive box">&nbsp;</div>
        </div>
        <div id="target" class="sibling box">&nbsp;</div>
    </div>
</body>
</html>