shiftRightUnsigned(numBits) {
    numBits &= 63;
    if (numBits == 0) {
      return this;
    } else {
      var high = this.high_;
      if (numBits < 32) {
        var low = this.low_;
        return Long.fromBits(
            (low >>> numBits) | (high << (32 - numBits)), high >>> numBits);
      } else if (numBits == 32) {
        return Long.fromBits(high, 0);
      } else {
        return Long.fromBits(high >>> (numBits - 32), 0);
      }
    }
  }
Returns this Long with bits shifted to the right by the given amount, with
zeros placed into the new leading bits.
@param {number} numBits The number of bits by which to shift.
@return {!Long} This shifted to the right by the given amount,
    with zeros placed into the new leading bits.