We're not animating. We can use the last render time and the scroll speed to work out whether
      // we actually need to paint anything yet. If not, we can return immediately.

      // Render at least every 1/6th of a second. The canvas may be resized, which there is
      // no reliable way to detect.
      var maxIdleMillis = Math.min(1000/6, this.options.millisPerPixel);

      if (nowMillis - this.lastRenderTimeMillis < maxIdleMillis) {
        return;
      }
    }

    this.resize();

    this.last