RenderTimeMillis = nowMillis;

    canvas = canvas || this.canvas;
    time = time || nowMillis - (this.delay || 0);

    // Round time down to pixel granularity, so motion appears smoother.
    time -= time % this.options.millisPerPixel;

    var context = canvas.getContext('2d'),
        chartOptions = this.options,
        dimensions = { top: 0, left: 0, width: canvas.clientWidth, height: canvas.clientHeight },
        // Calculate the threshold time for the oldest data points.
        oldestValidTime = 