I'm using `electron.systemPreferences.subscribeNotification` to listen for events coming from `NSDistributedNotificationCenter` in my app:

``` js
prefs.subscribeNotification('com.app.name.EventName', function(notification){
  console.log(notification)
})
```

This produces a single line of output in my log every time the event happens on my system, the only trouble is that the output is `undefined`. My expectation is that I would have access to the `NSNotification` object metadata as JSON.

When I subscribe to this notification in an Objective-C app, I get metadata with the event

``` obj-c
<0x618000000750>-[AppDelegate notify:]: object: com.app.name name: com.app.name.EventName userInfo: {
    Key = Value;
    ...
}
```

atom/browser/api/atom_api_system_preferences.h
public:
  static mate::Handle<SystemPreferences> Create(v8::Isolate* isolate);
  static void BuildPrototype(v8::Isolate* isolate,
                             v8::Local<v8::ObjectTemplate> prototype);
#if defined(OS_WIN)
  bool IsAeroGlassEnabled();
#elif defined(OS_MACOSX)
  int SubscribeNotification(const std::string& name,
                            const base::Closure& callback);
  void UnsubscribeNotification(int id);
  v8::Local<v8::Value> GetUserDefault(const std::string& name,
                                      const std::string& type);
#endif
  bool IsDarkMode();
 protected:
  explicit SystemPreferences(v8::Isolate* isolate);
  ~SystemPreferences() override;
 private:
  DISALLOW_COPY_AND_ASSIGN(SystemPreferences);
};
}  
}  
#endif