update ion-nav css

ionic/components/app/structure.scss

@@ -13,8 +13,8 @@ html {
   margin: 0;
   padding: 0;
 
-  .nav {
-    // container of many .nav-views, each .nav-view contains one view
+  ion-nav {
+    // container of header.toolbar-container, footer.toolbar-container and .nav-item-container
     position: absolute;
     top: 0;
     right: 0;
@@ -34,6 +34,7 @@ html {
     min-height: 50px;
     @include flex-order($flex-order-toolbar-top);
   }
+
   footer.toolbar-container {
     @include flex-order($flex-order-toolbar-bottom);
   }

ionic/components/nav/nav-base.js

@@ -9,7 +9,6 @@ export class NavBase {
     element: NgElement
   ) {
     this.domElement = element.domElement;
-    this.domElement.classList.add('nav');
 
     // this is our sane stack of items. This is synchronous and says an item
     // is removed even if it's still animating out.

ionic/components/tabs/test/advanced/main.html

@@ -3,7 +3,7 @@
   Hello! I'm a side menu in the root.
 </ion-aside> -->
 
-<ion-nav #viewport [initial]="initial">
+<ion-nav [initial]="initial">
 </ion-nav>