LayoutTests/fast/canvas/canvas-resize-reset-pixelRatio.html

<pre id="console"></pre>
<script>
    function log(message)
    {
        document.getElementById("console").appendChild(document.createTextNode(message + "\n"));
    }

    if (!window.testRunner)
        log("This test requires WebKitTestRunner or DumpRenderTree.");

    testRunner.dumpAsText();
    testRunner.waitUntilDone();

    var canvas = document.createElement("canvas");
    canvas.width = 8;
    canvas.height = 8;

    var context = canvas.getContext("2d");
    var cssContext = document.getCSSCanvasContext("2d", "test", 8, 8);

    if (context.webkitBackingStorePixelRatio !== 1)
        log("FAIL: expected webkitBackingStorePixelRatio of 1, was " + context.webkitBackingStorePixelRatio + ".");

    testRunner.setBackingScaleFactor(2, function() {
        var testCanvas = document.createElement("canvas");
        var testContext = testCanvas.getContext("2d");

        if (testContext.webkitBackingStorePixelRatio === 2) {
            log("Testing webkitBackingStorePixelRatio after resize");

            function assertPixelRatio(context, expected)
            {
                if (context.webkitBackingStorePixelRatio === expected)
                    log("PASS: webkitBackingStorePixelRatio is " + expected + ".");
                else
                    log("FAIL: webkitBackingStorePixelRatio is " + context.webkitBackingStorePixelRatio + ", expected " + expected + ".");
            }

            assertPixelRatio(context, 1);

            canvas.width = 8;
            canvas.height = 8;

            assertPixelRatio(context, 2);

            assertPixelRatio(cssContext, 1);

            cssContext = document.getCSSCanvasContext("2d", "test", 8, 8);

            assertPixelRatio(cssContext, 2);
        } else
            log("High-DPI canvas is not enabled.");

        testRunner.notifyDone();
    });
</script>