How to retain scroll position after forcing a controll refresh?

[Adam-Langley]

As per description, when I call refresh on the PagingController, the scroll position is reset to 0.
I would like to restore the users prior scroll position.

How can this be achieved?

Note: I'm using the PagedSliverList

Thanks,

[KrisBraun]

If you want a bi-directional list, this technique with forward and reverse lists works well.