Update or delete language tests using obsolete interfaces or default factory

tests/language/default_factory_library.dart

Index: tests/language/default_factory_library.dart
===================================================================
--- tests/language/default_factory_library.dart	(revision 15648)
+++ tests/language/default_factory_library.dart	(working copy)
@@ -1,4 +1,4 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
@@ -8,7 +8,7 @@
 import "default_factory_library_test.dart" as test;
 
 // References a factory class in another library
-interface A default test.C {
-  A();
+abstract class A {
+  factory A() = test.C.A;
   int methodA();
 }