Back out "Back out "[flipper][js] JS apps support 1/n""

Summary:
Original commit changeset: ff84080d43fa

This re-adds JS client support. The original version had a small bug that inadvertantly wrapped support for Android emulators in the dropdown in a GK that was only meant to cover JS clients. This is addressed here.

Reviewed By: timur-valiev

Differential Revision: D18707485

fbshipit-source-id: ceea8e279a21111f96073f8b784e852f6313e2a4

src/server.tsx

@@ -16,6 +16,7 @@ import {RSocketServer} from 'rsocket-core';
 import RSocketTCPServer from 'rsocket-tcp-server';
 import {Single} from 'rsocket-flowable';
 import Client from './Client';
+import {FlipperClientConnection} from './Client';
 import {UninitializedClient} from './UninitializedClient';
 import {reportPlatformFailures} from './utils/metrics';
 import EventEmitter from 'events';
@@ -23,9 +24,11 @@ import invariant from 'invariant';
 import tls from 'tls';
 import net, {Socket} from 'net';
 import {Responder, Payload, ReactiveSocket} from 'rsocket-types';
+import GK from './fb-stubs/GK';
+import {initJsEmulatorIPC} from './utils/js-client/serverUtils';
 
 type ClientInfo = {
-  connection: ReactiveSocket<any, any> | null | undefined;
+  connection: FlipperClientConnection<any, any> | null | undefined;
   client: Client;
 };
 
@@ -83,6 +86,11 @@ class Server extends EventEmitter {
         return;
       });
     reportPlatformFailures(this.initialisePromise, 'initializeServer');
+
+    if (GK.get('flipper_js_client_emulator')) {
+      initJsEmulatorIPC(this.store, this.logger, this, this.connections);
+    }
+
     return this.initialisePromise;
   }
 
@@ -303,7 +311,7 @@ class Server extends EventEmitter {
   }
 
   async addConnection(
-    conn: ReactiveSocket<any, any>,
+    conn: FlipperClientConnection<any, any>,
     query: ClientQuery,
     csrQuery: ClientCsrQuery,
   ): Promise<Client> {