Summary:
Fixed a longer standing issue where after a horizontal resize the rows wouldn't redraw until new data arrives (or the user scrolls), resulting in rendering artefacts.
Also introduced a hook to force a reflow of contents if the contents of a hook changes. It's a bit leaky abstraction, but does keep the virtualization performant if dynamic heights are used.
Reviewed By: passy
Differential Revision: D27395516
fbshipit-source-id: 1691af3ec64f1a476969a318553d83e22239997c
8cd38a6b49