Summary:
VirtualizedList state is represented in terms of [first, last] ranges, where it is possible to express a zero-cell range by having [n, n-1]. This includes some awkward examples, like [0, -1] being valid.
CellRenderMask assumes `addCells` is called with at least one cell, with VirtualizedList previously guarding against adding the no cell case. This guard is present for adding main cell regions, but not for `_initialRenderRegion()`, which can be overridden to have a zero length as well.
This moves the `CellRenderMask` to be permissive of zero-length cell regions, and removes the caller guard.
Changelog:
[Internal][Fixed] - Allow empty cell ranges in CellRenderMask
Reviewed By: rshest
Differential Revision: D38184444
fbshipit-source-id: d2dadfdd9628b24f894126d63b1eb93f6387b877
Nick Gerleman
0cfe5ae526