onLinesInserted(fromLineNumber, toLineNumber) {
        this._checkPendingChanges();
        fromLineNumber = fromLineNumber | 0;
        toLineNumber = toLineNumber | 0;
        this._lineCount += (toLineNumber - fromLineNumber + 1);
        for (let i = 0, len = this._arr.length; i < len; i++) {
            const afterLineNumber = this._arr[i].afterLineNumber;
            if (fromLineNumber <= afterLineNumber) {
                this._arr[i].afterLineNumber += (toLineNumber - fromLineNumber + 1);
            }
        }
    }
Notify the layouter that lines have been inserted (a continuous zone of lines).

@param fromLineNumber The line number at which the insertion started, inclusive
@param toLineNumber The line number at which the insertion ended, inclusive.