function _setTimelineUpdateTimer(){
            _unsetTimelineUpdateTimer();

            vars.timelineItems = _countTimelineItems();
            vars.timelineUpdateTimer = setInterval(function(){
                var isEditing = (elements.timelineWrap.find(".comment-update-form:visible").length > 0)
                                || _isDockedInspectorOpened();

                if(vars.isTimelineUpdating !== true && !isEditing){
                    _updateTimeline();
                }
            }, vars.timelineUpdatePeriod);
        }
Update timeline automatically with interval timer.
Don't update if visible .comment-update-form exists
or docked inspector is opened.

@private