Enable physical iOS devices in open source

Summary:
The last piece of the puzzle to get this working.

Now if a user has iOS development enabled in Flipper settings, and has XCode installed, we'll run the PortForwardingMacApp processes required to interact with iOS devices.

It's not great the way it starts the processes without any error checking, but since that's the way it currently works, I'm leaving it as it is for now.

Reviewed By: mweststrate

Differential Revision: D21881041

fbshipit-source-id: 1d1fdb7e0621cff88408bb707d768bb5c6bea0cc

desktop/app/src/dispatcher/iOSDevice.tsx

@@ -31,6 +31,8 @@ type iOSSimulatorDevice = {
 
 type IOSDeviceParams = {udid: string; type: DeviceType; name: string};
 
+let portForwarders: Array<ChildProcess> = [];
+
 function isAvailable(simulator: iOSSimulatorDevice): boolean {
   // For some users "availability" is set, for others it's "isAvailable"
   // It's not clear which key is set, so we are checking both.
@@ -55,10 +57,15 @@ function forwardPort(port: number, multiplexChannelPort: number) {
     `-multiplexChannelPort=${multiplexChannelPort}`,
   ]);
 }
-// start port forwarding server for real device connections
-const portForwarders: Array<ChildProcess> = GK.get('flipper_ios_device_support')
-  ? [forwardPort(8089, 8079), forwardPort(8088, 8078)]
-  : [];
+
+function startDevicePortForwarders(): void {
+  if (portForwarders.length > 0) {
+    // Only ever start them once.
+    return;
+  }
+  // start port forwarding server for real device connections
+  portForwarders = [forwardPort(8089, 8079), forwardPort(8088, 8078)];
+}
 
 if (typeof window !== 'undefined') {
   window.addEventListener('beforeunload', () => {
@@ -264,7 +271,11 @@ export default (store: Store, logger: Logger) => {
       store.dispatch(setXcodeDetected(isDetected));
       return isDetected;
     })
-    .then((isDetected) =>
-      isDetected ? queryDevicesForever(store, logger) : Promise.resolve(),
-    );
+    .then((isDetected) => {
+      if (isDetected) {
+        startDevicePortForwarders();
+        return queryDevicesForever(store, logger);
+      }
+      return Promise.resolve();
+    });
 };