_getLabelSize(label) {
    const ticksOpts = this.options.ticks;
    const tickLabelWidth = this.ctx.measureText(label).width;
    const angle = toRadians(this.isHorizontal() ? ticksOpts.maxRotation : ticksOpts.minRotation);
    const cosRotation = Math.cos(angle);
    const sinRotation = Math.sin(angle);
    const tickFontSize = this._resolveTickFontOptions(0).size;

    return {
      w: (tickLabelWidth * cosRotation) + (tickFontSize * sinRotation),
      h: (tickLabelWidth * sinRotation) + (tickFontSize * cosRotation)
    };
  }
@param {string} label
@return {{w:number, h:number}}
@private