Migrate test block 47 and downstream dependencies to Dart 2.0.

tests/language_2/class_cycle2_test.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.
 // Check fail because of cycles in super class relationship.
 
 class C extends B {}
 
 class A extends B {}
 
 class B
   extends A // //# 01: compile-time error
   extends A // //# 02: compile-time error
 {}
 
 main() {
   new C(); // //# 01: continued
   new List<C>(); // //# 02: continued
 }