Keep position after adding new items

Currently when adding new items (using infinite scroll) to the top of the list, the new Messages push down the old ones creating the impression of the messages jumping up. (That's standard html/js behaviour)
This library should properly handle keeping the view position consistent as new messages are added.

Start by locating the infinite-scroll message list and reproduce loading older messages at the top. Trace the list's scroll position before and after items are added; done means the visible messages remain in the same position instead of jumping upward.

Written by the indexing model from the issue text.