anchor.diff:      selector: 'd-navbar',
       styleUrls: const ['d_navbar.css'],
       templateUrl: 'd_navbar.html')
  -class NavbarComponent implements AfterViewInit {
  -  NavbarComponent(this.host) {
  -    _parentElement = host.parent;
  +class NavbarComponent implements OnInit, AfterViewInit {
  +  NavbarComponent(this.host);
  +
  +  @override
  +  void ngOnInit() {
  +    _parentElement = trackDocument ? window.document : host.parent;
       _parentElement.onScroll.listen((event) {
         if (alwaysShow)
           offset = 0;
  
positive.code: 
    @Input()
    bool alwaysShow = false;
  }
  
negative.code:     });
    }
  
    @override
    void ngAfterViewInit() {
      /**
       * Make sure nav doesn't overflow container scrollbar
  