Revert "Report errors on duplicate export."

tests/language/duplicate_import_libd.dart

Index: tests/language/duplicate_import_libd.dart
diff --git a/tests/language/duplicate_import_libd.dart b/tests/language/duplicate_import_libd.dart
deleted file mode 100644
index ccec81e0ff6df566051ae1aa52b7e8c4e6c6fc48..0000000000000000000000000000000000000000
--- a/tests/language/duplicate_import_libd.dart
+++ /dev/null
@@ -1,13 +0,0 @@
-// 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.
-
-library libd;
-
-import 'duplicate_import_liba.dart';
-import 'duplicate_import_libb.dart';
-import 'duplicate_import_libc.dart';
-
-export 'duplicate_import_liba.dart';
-export 'duplicate_import_libb.dart';
-export 'duplicate_import_libc.dart';