message: refactor(@nguniversal/common): remove redundant `toPromise()`
diff: * found in the LICENSE file at https://angular.io/license
  */
  import {
  - HTTP_INTERCEPTORS,
  HttpEvent,
  HttpHandler,
  HttpHeaders,
  HttpInterceptor,
  HttpParams,
  HttpRequest,
  - HttpResponse,
  + HttpResponse, HTTP_INTERCEPTORS
  } from '@angular/common/http';
  import { ApplicationRef, Injectable, NgModule } from '@angular/core';
  import {
  - BrowserTransferStateModule,
  - StateKey,
  - TransferState,
  - makeStateKey,
  + BrowserTransferStateModule, makeStateKey, StateKey,
  + TransferState
  } from '@angular/platform-browser';
  import { Observable, of as observableOf } from 'rxjs';
  import { filter, take, tap } from 'rxjs/operators';
  @@ -71,13 +68,10 @@ export class TransferHttpCacheInterceptor implements HttpInterceptor {
  // Stop using the cache if the application has stabilized, indicating initial rendering is
  // complete.
  // tslint:disable-next-line: no-floating-promises
  - appRef.isStable
  - .pipe(
  + appRef.isStable.pipe(
  filter((isStable: boolean) => isStable),
  take(1),
  - )
  - .toPromise()
  - .then(() => {
  + ).subscribe(() => {
  this.isCacheActive = false;
  });
  }
  