Fix result type checking of factory constructors of generic classes in VM.

tests/language/factory_redirection_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.
 
 class A<T> {
   A() : x = null;
 
   const A.constant(this.x);
 
   factory A.factory() {
@@ skipping 44 matching lines @@
 main() {
   new A<List>.test01();  /// 01: continued
   new A<List>.test02();  /// 02: continued
   new A<List>.test03();  /// 03: continued
   new C.test04();  /// 04: continued
   new B.test05(0);  /// 05: continued
   new C.test06<int, int>(0);  /// 06: continued
   new C.test07<int, int>(0);  /// 07: continued
   Expect.isTrue(new A<List>() is A<List>);
   Expect.isTrue(new A<bool>.constant(true).x);
-  Expect.isTrue(new A<List>.factory() is B<Set>);
+  Expect.isTrue(new A<Set>.factory() is B<Set>);
   Expect.isTrue(new B<List>.A() is A<List>);
   Expect.isTrue(new B<bool>.A_constant(true).x);
   Expect.isTrue(new B<List>.A_factory() is B<Set>);
   Expect.isTrue(new C<String, num>.A() is A<num>);
   Expect.isTrue(new C<String, num>.A_factory() is B<Set>);
   Expect.isTrue(new C<String, bool>.B_constant(true).x);
 }