Remove files that have already been ported or do not need to be ported.

client/html/src/MessagePortWrappingImplementation.dart

Index: client/html/src/MessagePortWrappingImplementation.dart
diff --git a/client/html/src/MessagePortWrappingImplementation.dart b/client/html/src/MessagePortWrappingImplementation.dart
deleted file mode 100644
index 63ec1d52a92e0885584c2dda28cc4dc6225adf5f..0000000000000000000000000000000000000000
--- a/client/html/src/MessagePortWrappingImplementation.dart
+++ /dev/null
@@ -1,7 +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.
-
-class MessagePortWrappingImplementation extends EventTargetWrappingImplementation implements MessagePort {
-  MessagePortWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
-}