LayoutTests/fast/canvas/font-update.html

<style>
    @font-face {
        font-family: no-such-font;
        src: url(no-such-file.ttf);
    }
</style>
<canvas id="target"></canvas>
<script>
    canvas = document.getElementById("target");
    ctx = canvas.getContext('2d');
    ctx.font = "100px no-such-font, ahem";
    ctx.fillStyle = "red";
    ctx.fillText("B", 0, 100);
    ctx.fillStyle = "green";
    canvas.parentNode.removeChild(canvas);
    if (window.layoutTestController) {
        layoutTestController.dumpAsText(true);
        layoutTestController.waitUntilDone();
	}
    setTimeout(function()
    {
        ctx.fillText("A", 0, 100);
        document.body.appendChild(canvas);
        if (window.layoutTestController)
            layoutTestController.notifyDone();
    }, 50);
</script>