Summary: public
Now if you scroll up out of the end threshold and then back down into it,
onEndReached will get triggered again. This closes https://github.com/facebook/react-native/issues/1967
This also resets onEndReached when the data source changes. This would fix
issues where the data source changes and onEndReached should fire again since
the new data may have more pages, whereas the old data had reached the end and
stopped.
Reviewed By: jingc
Differential Revision: D2610799
fb-gh-sync-id: f6cef513a42d4765514bf4bc55d9e31a760117f1
a4f7aa4853