Remove everything but markdown from third_party

third_party/pkg/js/lib/src/wrapping/util.dart

Index: third_party/pkg/js/lib/src/wrapping/util.dart
diff --git a/third_party/pkg/js/lib/src/wrapping/util.dart b/third_party/pkg/js/lib/src/wrapping/util.dart
deleted file mode 100644
index d658cbecee1f668cbf57c74475565c9ebb2f58ab..0000000000000000000000000000000000000000
--- a/third_party/pkg/js/lib/src/wrapping/util.dart
+++ /dev/null
@@ -1,9 +0,0 @@
-// Copyright (c) 2013, 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.
-
-part of js.wrapping;
-
-typedef T Mapper<F,T>(F o);
-
-dynamic mapNotNull(dynamic o, Mapper mapper) => o != null ? mapper(o) : null;