docs: function() {
        this.bounds.reset();
        if (this.slices.length) {
          this.bounds.addValue(this.slices[0].start);
          this.bounds.addValue(this.slices[this.slices.length - 1].end);
        }
        for (var id in this.counters) {
          this.counters[id].updateBounds();
          this.bounds.addRange(this.counters[id].bounds);
        }
        if (this.samples_ && this.samples_.length) {
          this.bounds.addValue(this.samples_[0].start);
          this.bounds.addValue(
              this.samples_[this.samples_.length - 1].end);
        }
      }