<html>
<head>
<script>
    function startTest() {
        if (window.testRunner) {
            testRunner.waitUntilDone();
            testRunner.setBackingScaleFactor(2, finishTest);
        }
    }
    
    function finishTest() {
        var test = document.getElementById("test");
        test.innerHTML = window.devicePixelRatio;
        setTimeout(function() { testRunner.notifyDone(); }, 0);
    }
</script>
</head>
<body onload="startTest();">
    <span style="background-color:red; -webkit-background-clip:text; -webkit-text-fill-color:transparent">This text should be nice and sharp. devicePixelRatio is: </span>
    <span id="test"></span>
</body>
</html>