.add('track');
    },

    get viewport() {
      return this.viewport_;
    },

    get drawingContainer() {
      if (this instanceof tr.ui.tracks.DrawingContainer) return this;
      let cur = this.parentElement;
      while (cur) {
        if (cur instanceof tr.ui.tracks.DrawingContainer) return cur;
        cur = cur.parentElement;
      }
      return undefined;
    },

    get eventContainer() {
    },

    invalidateDrawingContainer() {
      const dc = this.drawingContainer;
      if (dc) dc.invali