Summary:
We currently use `BatchedBridge.registerCallableModule` to call JS from platform code in a bunch of places (e.g. `RCTDeviceEventEmitter.emit()`), including some pretty essential ones - for example, Networking relies on `RCTDeviceEventEmitter` to emit events to JS for network requests and errors. In order to make the migration to bridgeless mode as easy as possible, it'd be best if we didn't have to update all the callsites in JS and platform code, at least for core JS modules like `RCTDeviceEventEmitter`. So we'd like to implement this callable module pattern for bridgeless mode as well.
In this diff, I'm installing a global variable, `RN$registerCallableModule`, which will store the JS module name and factory function in C++. This can then be called from platform code (Java/Obj-C) to invoke a JS function on a module using the existing APIs (`context.getJSModule()` on Android, `enqueueJSCall()` or similar on iOS).
Changelog: [Internal]
Reviewed By: PeteTheHeat
Differential Revision: D18798852
fbshipit-source-id: fbe9eaecaf6f5cab5173beec999d3a933b13375d
37ff892e24