refactor(router): make RouterLink and RouterLinkWithHref create url in a similar way

Author: vsavkin

modules/@angular/router/src/directives/router_link.ts

@@ -128,8 +128,6 @@ export class RouterLinkWithHref implements OnChanges, OnDestroy {
   // the url displayed on the anchor element.
   @HostBinding() href: string;
 
-  urlTree: UrlTree;
-
   constructor(
       private router: Router, private route: ActivatedRoute,
       private locationStrategy: LocationStrategy) {
@@ -167,17 +165,17 @@ export class RouterLinkWithHref implements OnChanges, OnDestroy {
   }
 
   private updateTargetUrlAndHref(): void {
-    this.urlTree = this.router.createUrlTree(this.commands, {
+    this.href = this.locationStrategy.prepareExternalUrl(this.router.serializeUrl(this.urlTree));
+  }
+
+  get urlTree(): UrlTree {
+    return this.router.createUrlTree(this.commands, {
       relativeTo: this.route,
       queryParams: this.queryParams,
       fragment: this.fragment,
       preserveQueryParams: toBool(this.preserveQueryParams),
       preserveFragment: toBool(this.preserveFragment)
     });
-
-    if (this.urlTree) {
-      this.href = this.locationStrategy.prepareExternalUrl(this.router.serializeUrl(this.urlTree));
-    }
   }
 }