Build Observatory as part of runtime

runtime/observatory/lib/src/elements/context_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 context_ref_element;
 
 import 'package:polymer/polymer.dart';
 import 'package:observatory/service.dart';
 import 'service_ref.dart';
 
@@ skipping 13 matching lines @@
         ref = result;
         notifyPropertyChange(#ref, 0, 1);
       }).whenComplete(onDone);
     } else {
       Context refMap = ref;
       refMap.variables = null;
       onDone();
     }
   }
 }