Summary:
`setupDevtools.js` is accessing `AppState.currentState` without checking its availability. In environments where 1) `__DEV__ == true`, and 2) no `RCTAppState` native module is provided thus resorting to `MissingNativeAppStateShim`, this will result in an exception:
```Cannot use 'AppState' module when native 'RCTAppState' is not included in the build. Either include it, or check 'AppState'.isAvailable before calling any methods.```
(Interestingly, `MissingNativeAppStateShim.currentState` did have a [default `null` value](118e88393e (diff-305b5180aa6ccc876ede6767de1fbfc4R192)) that was [later removed](a93b7a2da0 (diff-305b5180aa6ccc876ede6767de1fbfc4R186)).)
**Update**: Following cpojer's suggestion of reverting a93b7a2da0. Title also updated to reflect this.
[General] [Fixed] - Remove MissingNativeRCTNetworkingShim; revert MissingNativeAppStateShim
Pull Request resolved: https://github.com/facebook/react-native/pull/24380
Differential Revision: D14932658
Pulled By: cpojer
fbshipit-source-id: aef7ca566b3b8660eaed74a8ba3b6b0117b1200c
57c1a7add2