Normalizes the view-sequence node so that the view-sequence is near to 0.
function _normalizePrevViewSequence(scrollOffset) {
        var count = 0;
        var normalizedScrollOffset = scrollOffset;
        var normalizeNextPrev = false;
        var node = this._nodes.getStartEnumNode(false);
        while (node) {
            if (!node._invalidated || !node._viewSequence) {
                break;
            }
            if (normalizeNextPrev) {
                this._viewSequence = node._viewSequence;
                normalizedScrollOffset = scrollOffset;
                normalizeNextPrev = false;
            }
            if ((node.scrollLength === undefined) || node.trueSizeRequested || (scrollOffset < 0)) {
                break;
            }
            scrollOffset -= node.scrollLength;
            count++;
            if (node.scrollLength) {
                if (this.options.alignment) {
                    normalizeNextPrev = (scrollOffset >= 0);
                }
                else {
                    if (Math.round(scrollOffset) >= 0) {
                        this._viewSequence = node._viewSequence;
                        normalizedScrollOffset = scrollOffset;
                    }
                }
            }
            node = node._prev;
        }
        return normalizedScrollOffset;
    }