Implement Evaluate without creating new classes.

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.
 
 import "dart:collection";
 
 final emptyList = new UnmodifiableListView([]);
 final emptyMap = new UnmodifiableMapView({});
@@ skipping 382 matching lines @@
   }
 
   InstanceMirror setField(Symbol memberName, arg) {
     var unwrapped = _n(memberName);
     var f = _setFieldClosures[unwrapped];
     return (f == null)
         ? _setFieldSlow(unwrapped, arg)
         : reflect(f(_reflectee, arg));
   }
 
+  eval(e) => _eval(e, null);
   static _eval(expression, privateKey)
       native "Mirrors_evalInLibraryWithPrivateKey";
 
   // Override to include the receiver in the arguments.
   InstanceMirror invoke(Symbol memberName,
                         List positionalArguments,
                         [Map<Symbol, dynamic> namedArguments]) {
     int numPositionalArguments = positionalArguments.length + 1;  // Receiver.
     int numNamedArguments = namedArguments != null ? namedArguments.length : 0;
     int numArguments = numPositionalArguments + numNamedArguments;
@@ skipping 1174 matching lines @@
     if (typeMirror == null) {
       typeMirror = makeLocalTypeMirror(key);
       _instanitationCache[key] = typeMirror;
       if (typeMirror is ClassMirror && !typeMirror._isGeneric) {
         _declarationCache[key] = typeMirror;
       }
     }
     return typeMirror;
   }
 }