chromium/third_party/blink/web_tests/compositing/tiled-layers-hidpi.html

<html>
    <style>
        #composited {
            width: 1800px;
            height: 10px;
            will-change: transform;
            background-color: blue;
        }
    </style>
    <script>
        function startTest() {
            if (window.testRunner) {
                testRunner.waitUntilDone();
                testRunner.dumpAsText();
                testRunner.setBackingScaleFactor(2, finishTest);
            }
        }
        
        function finishTest() {
            setTimeout(function() {
                document.getElementById('layer-tree').innerText = internals.layerTreeAsText(document);
                testRunner.notifyDone();
            }, 0);
        }
        </script>
    </head>
    <body onload="startTest();">
        <div id="composited"></div>
<pre id="layer-tree">Layer tree goes here in DRT</pre>
    </body>
</html>