constructor(spriter) {
    super();

    this._spriter = spriter;
    this._files = [];
    this.active = 0;

    this.on('add', this.process.bind(this));
    this.on('remove', this.process.bind(this));

    this._spriter.debug('Created processing queue instance');
  }
SVGSpriter queue

@param {SVGSpriter} spriter          SVGSpriter instance