Use Chain.capture instead of runZoned

runtime/observatory/lib/src/elements/instance_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.
 
 import 'dart:html';
 import 'dart:async';
 import 'package:observatory/models.dart' as M;
 import 'package:observatory/src/elements/curly_block.dart';
 import 'package:observatory/src/elements/field_ref.dart';
 import 'package:observatory/src/elements/helpers/any_ref.dart';
 import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
 import 'package:observatory/src/elements/helpers/tag.dart';
 import 'package:observatory/src/elements/helpers/uris.dart';
-import 'package:observatory/src/elements/sentinel_value.dart';
 import 'package:observatory/utils.dart';
 
 class InstanceRefElement extends HtmlElement implements Renderable {
   static const tag = const Tag<InstanceRefElement>('instance-ref');
 
   RenderingScheduler<InstanceRefElement> _r;
 
   Stream<RenderedEvent<InstanceRefElement>> get onRendered => _r.onRendered;
 
   M.IsolateRef _isolate;
@@ skipping 279 matching lines @@
           new BRElement(),
           new SpanElement()..text = '<value> : ',
           new InstanceRefElement(_isolate, _loadedInstance.value, _instances,
               queue: _r.queue),
         ];
       default:
         return [];
     }
   }
 }