moveRows(dst, src, count) {
    if (src < 0 || dst < 0) {
      return;
    }

    if (dst >= src) {
      for (let i = count-1; i >= 0; i--) {
        this.rows_[dst + i] = this.rows_[src + i].map((e) => e);
      }
    } else {
      for (let i = 0; i < count; i++) {
        this.rows_[dst + i] = this.rows_[src + i].map((e) => e);
      }
    }
  }
Moves rows of characters.
@param {number} dst Destination row index.
@param {number} src Source row index.
@param {number} count Count of rows to move.