offset(offset) {
    if (this.minSegmentStartTime_ != null) {
      this.minSegmentStartTime_ += offset;
    }
    if (this.maxSegmentEndTime_ != null) {
      this.maxSegmentEndTime_ += offset;
    }
  }
Offsets the segment times by the given amount.

@param {number} offset The number of seconds to offset by.  A positive
  number adjusts the segment times forward.
@export