Build Observatory as part of runtime

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

 // Copyright (c) 2014, 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 vm_connect_element;
 
 import 'dart:html';
 import 'package:polymer/polymer.dart';
 import 'observatory_element.dart';
 import 'package:observatory/app.dart';
@@ skipping 97 matching lines @@
           // This happens when a tab has devtools open!
           continue;
         }
         chromeTargets.add(targets[i]);
       }
     }).catchError((e) {
       chromeTargets.clear();
     });
   }
 }