._scrollPositionMap;
        if (oldSubroute != null && oldSubroute.prefix != null) {
          // Don't reset the scroll position in the detail page.
          if (oldSubroute.prefix.indexOf('detail') == -1) {
            map[oldSubroute.prefix] = window.pageYOffset;
          }
        }
        if (map[subroute.prefix] != null) {
          Polymer.AppLayout.scroll({ top: map[subroute.prefix], behavior: 'silent' });
        } else if (this.isAttached) {
          Polymer.AppLayout.scroll({ top: 0, behavio