setTicks(majorUnits, minorUnits) {
    this.majorTicks_ = Math.max(1, majorUnits);
    this.minorTicks_ = Math.max(1, minorUnits);
    this.draw_();
  }
Sets the number of major tick sections and minor tick sections.
@param {number} majorUnits The number of major tick sections.
@param {number} minorUnits The number of minor tick sections for each major
    tick section.