VM: Support calling through getters in InstanceMirror.delegate. Implement without accessing private…

tests/language/invocation_mirror2_test.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.
 
 import "dart:mirrors" show reflect;
 import "package:expect/expect.dart";
 
 class GetName {
   set flif(_) => "flif=";
 }
 
-String getName(im) => reflect(new GetName()).delegate(im);
+int getName(im) => reflect(new GetName()).delegate(im);
 
 class C {
   var im;
   noSuchMethod(im) => this.im = im;
   flif() {}
 }
 
 main() {
  var c = new C();
  c.flif = 42;
- Expect.equals('flif=', getName(c.im));
+ Expect.equals(42, getName(c.im));
  Expect.equals(42, c.im.positionalArguments[0]);
 }