Summary:
This adds support for a controlled `selection` prop on `TextInput` on iOS (Android PR coming soon). This is based on the work by ehd in #2668 which hasn't been updated for a while, kept the original commit and worked on fixing what was missing based on the feedback in the original PR.
What I changed is:
- Make the prop properly controlled by JS
- Add a RCTTextSelection class to map the JS object into and the corresponding RCTConvert category
- Make sure the selection change event is properly triggered when the input is focused
- Cleanup setSelection
- Changed TextInput to use function refs to appease the linter
** Test plan **
Tested using the TextInput selection example in UIExplorer on iOS.
Also tested that it doesn't break Android.
Closes https://github.com/facebook/react-native/pull/8958
Differential Revision: D3771229
Pulled By: javache
fbshipit-source-id: b8ede46b97fb3faf3061bb2dac102160c4b20ce7
f0a3c56048