Converted Observatory nav-menu element

runtime/observatory/lib/elements.dart

 library observatory_elements;
 
 // Export elements.
 export 'package:observatory/src/elements/action_link.dart';
 export 'package:observatory/src/elements/class_ref.dart';
 export 'package:observatory/src/elements/class_tree.dart';
 export 'package:observatory/src/elements/class_view.dart';
 export 'package:observatory/src/elements/code_ref.dart';
 export 'package:observatory/src/elements/code_view.dart';
 export 'package:observatory/src/elements/context_ref.dart';
@@ skipping 43 matching lines @@
 export 'package:observatory/src/elements/service_ref.dart';
 export 'package:observatory/src/elements/service_view.dart';
 export 'package:observatory/src/elements/sliding_checkbox.dart';
 export 'package:observatory/src/elements/timeline_page.dart';
 export 'package:observatory/src/elements/vm_connect.dart';
 export 'package:observatory/src/elements/vm_ref.dart';
 export 'package:observatory/src/elements/vm_view.dart';
 
 import 'dart:async';
 
+import 'package:observatory/src/elements/nav/menu.dart';
+import 'package:observatory/src/elements/nav/menu_wrapper.dart';
 import 'package:observatory/src/elements/view_footer.dart';
 
 export 'package:observatory/src/elements/helpers/rendering_queue.dart';
 
+export 'package:observatory/src/elements/nav/menu.dart';
 export 'package:observatory/src/elements/view_footer.dart';
 
 // Even though this function does not invoke any asynchronous operation
 // it is marked as async to allow future backward compatible changes.
 Future initElements() async {
+  NavMenuElement.tag.ensureRegistration();
+  NavMenuElementWrapper.tag.ensureRegistration();
   ViewFooterElement.tag.ensureRegistration();
 }