message: feat(router): add a function set up router sync when used with downgradeModule
diff: * found in the LICENSE file at https://angular.io/license
  */
  -import {APP_BOOTSTRAP_LISTENER, ComponentRef, InjectionToken} from '@angular/core';
  +import {APP_BOOTSTRAP_LISTENER, ComponentRef, InjectionToken, Injector} from '@angular/core';
  import {Router} from '@angular/router';
  import {UpgradeModule} from '@angular/upgrade/static';
  @@ -50,7 +50,7 @@ export function locationSyncBootstrapListener(ngUpgrade: UpgradeModule) {
  }
  /**
  - * @whatItDoes Sets up a location synchronization.
  + * @whatItDoes Sets up a location synchronization using the provided UpgradeModule.
  *
  * History.pushState does not fire onPopState, so the Angular location
  * doesn't detect it. The workaround is to attach a location change listener
  @@ -64,12 +64,22 @@ export function setUpLocationSync(ngUpgrade: UpgradeModule) {
  Remove RouterUpgradeInitializer and call setUpLocationSync after UpgradeModule.bootstrap.
  `);
  }
  + setUpRouterSync(ngUpgrade.injector, ngUpgrade.$injector);
  +}
  - const router: Router = ngUpgrade.injector.get(Router);
  +/**
  + * @whatItDoes Sets up a router synchronization using the Angular and AngularJS injectors.
  + *
  + * History.pushState does not fire onPopState, so the Angular location
  + * doesn't detect it. The workaround is to attach a location change listener
  + *
  + * @experimental
  + */
  +export function setUpRouterSync(injector: Injector, $injector: any) {
  + const router: Router = injector.get(Router);
  const url = document.createElement('a');
  - ngUpgrade.$injector.get('$rootScope')
  - .$on('$locationChangeStart', (_: any, next: string, __: string) => {
  + $injector.get('$rootScope').$on('$locationChangeStart', (_: any, next: string, __: string) => {
  url.href = next;
  router.navigateByUrl(url.pathname + url.search + url.hash);
  });
  