How to use the @angular/fire.FirebaseZoneScheduler function in @angular/fire

export function FirebaseObjectFactory (
  ref: DatabaseReference,
  { preserveSnapshot }: FirebaseObjectFactoryOpts = {}): FirebaseObjectObservable {

  const objectObservable = new FirebaseObjectObservable((obs: Observer) => {
    let fn = ref.on('value', (snapshot: DataSnapshot) => {
      obs.next(preserveSnapshot ? snapshot : utils.unwrapMapFn(snapshot))
    }, err => {
      if (err) { obs.error(err); obs.complete(); }
    });

    return () => ref.off('value', fn);
  }, ref);

  // TODO: should be in the subscription zone instead
  return observeOn.call(objectObservable, new FirebaseZoneScheduler(new NgZone({}), {}));
}

constructor(
    @Inject(FirebaseOptionsToken) options:FirebaseOptions,
    @Optional() @Inject(FirebaseNameOrConfigToken) nameOrConfig:string|FirebaseAppConfig|null|undefined,
    @Inject(PLATFORM_ID) platformId: Object,
    private zone: NgZone
  ) {
    const scheduler = new FirebaseZoneScheduler(zone, platformId);
    this.auth = zone.runOutsideAngular(() => {
      const app = _firebaseAppFactory(options, zone, nameOrConfig);
      return app.auth();
    });

    this.authState = scheduler.keepUnstableUntilFirst(
      scheduler.runOutsideAngular(
        new Observable(subscriber => {
          const unsubscribe = this.auth.onAuthStateChanged(subscriber);
          return { unsubscribe };
        })
      )
    );

    this.user = scheduler.keepUnstableUntilFirst(
      scheduler.runOutsideAngular(

constructor(
    @Inject(FirebaseOptionsToken) options:FirebaseOptions,
    @Optional() @Inject(FirebaseNameOrConfigToken) nameOrConfig:string|FirebaseAppConfig|null|undefined,
    @Optional() @Inject(RealtimeDatabaseURL) databaseURL:string|null,
    @Inject(PLATFORM_ID) platformId: Object,
    zone: NgZone
  ) {
    this.scheduler = new FirebaseZoneScheduler(zone, platformId);
    this.database = zone.runOutsideAngular(() => {
      const app = _firebaseAppFactory(options, zone, nameOrConfig);
      return app.database(databaseURL || undefined);
    });
  }

constructor(
    @Inject(FirebaseOptionsToken) options:FirebaseOptions,
    @Optional() @Inject(FirebaseNameOrConfigToken) nameOrConfig:string|FirebaseAppConfig|null|undefined,
    @Inject(PLATFORM_ID) platformId: Object,
    zone: NgZone,
    @Optional() @Inject(FUNCTIONS_REGION) region:string|null,
    @Optional() @Inject(FUNCTIONS_ORIGIN) origin:string|null
  ) {
    this.scheduler = new FirebaseZoneScheduler(zone, platformId);
    
    this.functions = zone.runOutsideAngular(() => {
      const app = _firebaseAppFactory(options, zone, nameOrConfig);
      return app.functions(region || undefined);
    });

    if (origin) {
      this.functions.useFunctionsEmulator(origin);
    }

  }

constructor(
    @Inject(FirebaseOptionsToken) options:FirebaseOptions,
    @Optional() @Inject(FirebaseNameOrConfigToken) nameOrConfig:string|FirebaseAppConfig|null|undefined,
    @Optional() @Inject(StorageBucket) storageBucket:string|null,
    @Inject(PLATFORM_ID) platformId: Object,
    zone: NgZone
  ) {
    this.scheduler = new FirebaseZoneScheduler(zone, platformId);
    this.storage = zone.runOutsideAngular(() => {
      const app = _firebaseAppFactory(options, zone, nameOrConfig);
      return app.storage(storageBucket || undefined);
    });
  }