Build Observatory as part of runtime

runtime/observatory/lib/src/elements/nav_bar.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library nav_bar_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'observatory_element.dart';
 import 'package:observatory/service.dart';
@@ skipping 134 matching lines @@
     app.removePauseEvents(event.isolate);
     return event.isolate.stepOut();
   }
 
   void closeItem(MouseEvent e, var detail, Element target) {
     events.remove(event);
   }
 
   NavNotifyItemElement.created() : super.created();
 }