h, dimensions.height);
    context.fillRect(0, 0, dimensions.width, dimensions.height);
    context.restore();

    // Grid lines...
    context.save();
    context.lineWidth = chartOptions.grid.lineWidth;
    context.strokeStyle = chartOptions.grid.strokeStyle;
    // Vertical (time) dividers.
    if (chartOptions.grid.millisPerLine > 0) {
      context.beginPath();
      for (var t = time - (time % chartOptions.grid.millisPerLine);
           t >= oldestValidTime;
           t -= chartOptions.grid.millisP