Remove stale files from lib/html/src.

lib/html/src/MessageEvent.dart

Index: lib/html/src/MessageEvent.dart
diff --git a/lib/html/src/MessageEvent.dart b/lib/html/src/MessageEvent.dart
deleted file mode 100644
index c909730a8e0fee7ec7817ff56e36cc4b7073bacf..0000000000000000000000000000000000000000
--- a/lib/html/src/MessageEvent.dart
+++ /dev/null
@@ -1,19 +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.
-
-interface MessageEvent extends Event default MessageEventWrappingImplementation {
-
-  MessageEvent(String type, String data, String origin, String lastEventId,
-      Window source, MessagePort port, [bool canBubble, bool cancelable]);
-
-  String get data();
-
-  String get lastEventId();
-
-  MessagePort get messagePort();
-
-  String get origin();
-
-  Window get source();
-}