Fix member overriding rules in VM according to latest spec.

tests/language/src/FieldOverrideTest.dart

 // Copyright (c) 2011, 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.
 
 // Test overriding of fields.
 
 interface A {}
 interface B1 extends A {}
 interface B2 extends A {}
 
 class Super {
   Super() : super();
 
   B1 field;
 }
 
 class Sub extends Super {
   Sub() : super();
 
-  A field;
+  A field;  /// 01: compile-time error
 }
 
 class SubSub extends Super {
   SubSub() : super();
 
-  B2 field; /// 01: static type error
+  B2 field;  /// 02: compile-time error
 }
 
 main() {
   new SubSub();
 }