Resubmission of native memory allocation info surfacing in Observatory. Fixed crashing tests and st…

runtime/observatory/lib/src/elements/class_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/helpers/rendering_scheduler.dart';
 import 'package:observatory/src/elements/helpers/tag.dart';
 import 'package:observatory/src/elements/helpers/uris.dart';
 
 class ClassRefElement extends HtmlElement implements Renderable {
   static const tag = const Tag<ClassRefElement>('class-ref');
 
   RenderingScheduler<ClassRefElement> _r;
 
   Stream<RenderedEvent<ClassRefElement>> get onRendered => _r.onRendered;
 
   M.IsolateRef _isolate;
   M.ClassRef _class;
 
   M.IsolateRef get isolate => _isolate;
   M.ClassRef get cls => _class;
 
   factory ClassRefElement(M.IsolateRef isolate, M.ClassRef cls,
       {RenderingQueue queue}) {
-    assert(isolate != null);
     assert(cls != null);
     ClassRefElement e = document.createElement(tag.name);
     e._r = new RenderingScheduler(e, queue: queue);
     e._isolate = isolate;
     e._class = cls;
     return e;
   }
 
   ClassRefElement.created() : super.created();
 
   @override
   void attached() {
     super.attached();
     _r.enable();
   }
 
   @override
   void detached() {
     super.detached();
     _r.disable(notify: true);
     children = [];
   }
 
   void render() {
     children = [
-      new AnchorElement(href: Uris.inspect(_isolate, object: _class))
-        ..text = _class.name
+      new AnchorElement(
+          href: (_isolate == null)
+              ? null
+              : Uris.inspect(_isolate, object: _class))..text = _class.name
     ];
   }
 }