refactor(navbar): improved navbar transitions

ionic/components/nav/view-controller.ts

@@ -325,6 +325,17 @@ export class ViewController {
     }
   }
 
+  /**
+   * TODO
+   * @returns {TODO} TODO
+   */
+  navbarBackgroundRef() {
+    let navbarView = this.navbarView();
+    if (navbarView) {
+      return navbarView.getNativeElement().querySelector('.toolbar-background');
+    }
+  }
+
   /**
    * TODO
    * @returns {TODO} TODO