AddModifiedElement(originalIndex, modifiedIndex) {
        // The 'true' start index is the smallest of the ones we've seen
        this.m_originalStart = Math.min(this.m_originalStart, originalIndex);
        this.m_modifiedStart = Math.min(this.m_modifiedStart, modifiedIndex);
        this.m_modifiedCount++;
    }
Adds the modified element at the given position to the elements
affected by the current change. The original index gives context
to the change position with respect to the modified sequence.
@param originalIndex The index of the original element that provides corresponding position in the original sequence.
@param modifiedIndex The index of the modified element to add.