Improve the instance-view page in observatory.

runtime/bin/vmservice/client/lib/src/elements/observatory_element.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 observatory_element;
 
 import 'dart:math';
 import 'package:polymer/polymer.dart';
 
 /// Base class for all Observatory custom elements.
@@ skipping 79 matching lines @@
 
   String fileAndLine(Map frame) {
     var file = frame['script']['user_name'];
     var shortFile = file.substring(file.lastIndexOf('/') + 1);
     return "${shortFile}:${frame['line']}";
   }
 
   bool isNull(String type) {
     return type == 'Null';
   }
+  
+  bool isError(String type) {
+    return type == 'Error';
+  }
 
   bool isInt(String type) {
     return (type == 'Smi' ||
             type == 'Mint' ||
             type == 'Bigint');
   }
 
   bool isBool(String type) {
     return type == 'Bool';
   }
@@ skipping 18 matching lines @@
   bool isUnexpected(String type) {
     return (!['Null',
               'Smi',
               'Mint',
               'Biginit',
               'Bool',
               'String',
               'Closure',
               'Instance',
               'GrowableObjectArray',
-              'Array'].contains(type));
+              'Array',
+              'Error'].contains(type));
   }
 }