Build Observatory as part of runtime

runtime/observatory/lib/src/elements/code_ref.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 code_ref_element;
 
 import 'package:polymer/polymer.dart';
 import 'service_ref.dart';
 import 'package:observatory/service.dart';
 
 @CustomTag('code-ref')
 class CodeRefElement extends ServiceRefElement {
   @observable Code get code => ref;
 
   refChanged(oldValue) {
     super.refChanged(oldValue);
     notifyPropertyChange(#code, 0, 1);
   }
 
   CodeRefElement.created() : super.created();
 }