Build Observatory as part of runtime

runtime/observatory/lib/src/elements/isolate_profile.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 isolate_profile_element;
 
 import 'dart:html';
 import 'observatory_element.dart';
 import 'package:logging/logging.dart';
 import 'package:observatory/service.dart';
@@ skipping 190 matching lines @@
     if (row is TableRowElement) {
       // Subtract 1 to get 0 based indexing.
       try {
         tree.toggle(row.rowIndex - 1);
       }  catch (e, stackTrace) {
         Logger.root.warning('toggleExpanded', e, stackTrace);
       }
     }
   }
 }