Add a VM defined class MirrorReference as an opaque pointer for Dart code to VM internal objects.

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 138 matching lines @@
       _rootLibrary = _rootLibrary.resolve(mirrors);
     }
     return _rootLibrary;
   }
 
   String toString() => "IsolateMirror on '$debugName'";
 }
 
 // A VMReference is used to hold a reference to a VM-internal object,
 // which can include things like libraries, classes, etc.
-class VMReference extends NativeFieldWrapperClass1 {
+class OldVMReference extends NativeFieldWrapperClass1 {
 }
 
 abstract class _LocalVMObjectMirrorImpl extends _LocalMirrorImpl {
   _LocalVMObjectMirrorImpl(this._reference) {}
 
   // For now, all VMObjects hold a VMReference.  We could consider
   // storing the Object reference itself here if the object is a Dart
   // language objects (except for objects of type VMReference, of
   // course).
-  VMReference _reference;
+  OldVMReference _reference;
 }
 
 abstract class _LocalObjectMirrorImpl extends _LocalVMObjectMirrorImpl
     implements ObjectMirror {
   _LocalObjectMirrorImpl(ref) : super(ref) {}
 
   InstanceMirror invoke(Symbol memberName,
                         List positionalArguments,
                         [Map<Symbol, dynamic> namedArguments]) {
     if (namedArguments != null) {
@@ skipping 857 matching lines @@
   }
 
   // Creates a new local ClassMirror.
   static ClassMirror makeLocalClassMirror(Type key)
       native "Mirrors_makeLocalClassMirror";
 
   static ClassMirror reflectClass(Type key) {
     return makeLocalClassMirror(key);
   }
 }