Migrate test block 47 and downstream dependencies to Dart 2.0.

tests/language_2/class_cycle_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.
 // Check fail because of cycles in super class relationship.
 
 import "package:expect/expect.dart";
 
 class Foo implements Bar {}
 
 class C {}
@@ skipping 11 matching lines @@
 // of a class C appears in the implements clause of C.
 class ExtendsC extends C
 implements C // //# 03: compile-time error
 {}
 
 main() {
   Expect.isTrue(new Foo() is Foo);
   Expect.isTrue(new ImplementsC() is C);
   Expect.isTrue(new ExtendsC() is C);
 }