Small fix for _LocalMirrorSystemImpl.toString().

runtime/lib/mirrors_impl.dart

 // Copyright (c) 2012, 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.
 
 // VM-specific implementation of the dart:mirrors library.
 
 // These values are allowed to be passed directly over the wire.
 bool isSimpleValue(var value) {
   return (value === null || value is num || value is String || value is bool);
 }
@@ skipping 29 matching lines @@
 
   TypeMirror get voidType() {
     if (_voidType === null) {
       _voidType =
           new _LocalClassMirrorImpl(
               null, 'void', false, null, null, [], null, const {});
     }
     return _voidType;
   }
 
-  String toString() => "MirrorSystem for isolate '$debugName'";
+  String toString() => "MirrorSystem for isolate '${isolate.debugName}'";
 }
 
 abstract class _LocalMirrorImpl implements Mirror {
   int hashCode() {
     throw new NotImplementedException('Mirror.hashCode() not yet implemented');
   }
 
   // Local mirrors always return the same MirrorSystem.  This field
   // is more interesting once we implement remote mirrors.
   MirrorSystem get mirrors() => _Mirrors.currentMirrorSystem();
@@ skipping 703 matching lines @@
 
   // Creates a new local InstanceMirror
   static InstanceMirror makeLocalInstanceMirror(Object reflectee)
       native 'Mirrors_makeLocalInstanceMirror';
 
   // Creates a new local mirror for some Object.
   static InstanceMirror reflect(Object reflectee) {
     return makeLocalInstanceMirror(reflectee);
   }
 }