Remove last 'extra_snippet'

client/dom/snippets/html/WindowImpl.dart.snippet

Index: client/dom/snippets/html/WindowImpl.dart.snippet
diff --git a/client/dom/snippets/html/WindowImpl.dart.snippet b/client/dom/snippets/html/WindowImpl.dart.snippet
deleted file mode 100644
index fff062bc7bf281165f181f7fd83e6dc4b6864143..0000000000000000000000000000000000000000
--- a/client/dom/snippets/html/WindowImpl.dart.snippet
+++ /dev/null
@@ -1,9 +0,0 @@
-// 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.
-
-// TODO(vsm): Should we add this to the API?  Dart doesn't support
-// overloading.
-// Window open(String url, String target, WindowSpec features) {
-//   return open(url, target, features.toString());
-// }