Give instances their own model class; move DartErrors out of instance-ref into their own error-ref.

runtime/bin/vmservice/observatory/lib/src/elements/service_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 service_ref_element;
 
 import 'dart:html';
 import 'package:logging/logging.dart';
 import 'package:polymer/polymer.dart';
 import 'observatory_element.dart';
@@ skipping 48 matching lines @@
 
 
 @CustomTag('any-service-ref')
 class AnyServiceRefElement extends ObservatoryElement {
   @published ServiceObject ref;
   AnyServiceRefElement.created() : super.created();
 
   Element _constructElementForRef() {
     var type = ref.serviceType;
     switch (type) {
-      case 'Class':
+      case 'Error':
+        ServiceRefElement element = new Element.tag('error-ref');
+        element.ref = ref;
+        return element;
+     case 'Class':
         ServiceRefElement element = new Element.tag('class-ref');
         element.ref = ref;
         return element;
       case 'Code':
         ServiceRefElement element = new Element.tag('code-ref');
         element.ref = ref;
         return element;
       case 'Field':
         ServiceRefElement element = new Element.tag('field-ref');
         element.ref = ref;
@@ skipping 38 matching lines @@
     var type = ref.serviceType;
     var element = _constructElementForRef();
     if (element == null) {
       Logger.root.info('Unable to find a ref element for \'${type}\'');
       return;
     }
     children.add(element);
     Logger.root.info('Viewing object of \'${type}\'');
   }
 }