Tabs.FlatList data not re-rendering when `extraData` is provided

[alexpchin]

Current behavior

I'm optimistically modifying some data in:

<Tabs.FlatList
      data={hits}
      extraData={_getMergedHits()}
      .
      .

However, the data doesn't seem to be re-rendering. If I modify the data in data then it works, e.g.

<Tabs.FlatList
      data={_getMergedHits()}
      .
      .

Expected behaviour

I expect the list data to update when modified data is passed to extraData