<!DOCTYPE html>
<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>
<script>
    function finishTest() {
        var test = document.getElementById("test");
        test.innerHTML = window.devicePixelRatio;
        setTimeout(function() { testRunner.notifyDone(); }, 0);
    }
    if (window.testRunner) {
        testRunner.waitUntilDone();
        testRunner.setBackingScaleFactor(2, finishTest);
    }
</script>