Add method field to persistedStateReducer

Summary:
When sending a message from the mobile side, you call something like:

`send(method: string, params: Object)`

But when receiving it in the reducer, you only get the params. Adding method so you can distinguish them.

Reviewed By: passy

Differential Revision: D10447890

fbshipit-source-id: f1fe925e82355866f86b322ecd3c72c604ae86af

src/Client.js

@@ -173,6 +173,7 @@ export default class Client extends EventEmitter {
           // $FlowFixMe: We checked persistedStateReducer exists
           const newPluginState = persistingPlugin.persistedStateReducer(
             persistedState,
+            params.method,
             params.params,
           );
           this.store.dispatch(