Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/MessageEvent.dartdoc

-// 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.
-
-// WARNING:
-//   This file contains documentation that is merged into the real source.
-//   Do not make code changes here.
-
-/// @domName MessageEvent
-interface MessageEvent extends Event {
-
-  /** @domName MessageEvent.data */
-  final Object data;
-
-  /** @domName MessageEvent.lastEventId */
-  final String lastEventId;
-
-  /** @domName MessageEvent.origin */
-  final String origin;
-
-  /** @domName MessageEvent.ports */
-  final List ports;
-
-  /** @domName MessageEvent.source */
-  final Window source;
-
-  /** @domName MessageEvent.initMessageEvent */
-  void initMessageEvent(String typeArg, bool canBubbleArg, bool cancelableArg, Object dataArg, String originArg, String lastEventIdArg, Window sourceArg, List messagePorts);
-
-  /** @domName MessageEvent.webkitInitMessageEvent */
-  void webkitInitMessageEvent(String typeArg, bool canBubbleArg, bool cancelableArg, Object dataArg, String originArg, String lastEventIdArg, Window sourceArg, List transferables);
-}