Get rid of a lot of () for getters.

lib/html/src/MessageEventWrappingImplementation.dart

 // 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 MessageEventWrappingImplementation extends EventWrappingImplementation implements MessageEvent {
   MessageEventWrappingImplementation._wrap(ptr) : super._wrap(ptr);
 
   factory MessageEventWrappingImplementation(String type, String data,
       String origin, String lastEventId, Window source, MessagePort port,
       [bool canBubble = true, bool cancelable = true]) {
     final e = dom.document.createEvent("MessageEvent");
     e.initMessageEvent(type, canBubble, cancelable, data, origin, lastEventId,
         LevelDom.unwrap(source), LevelDom.unwrap(port));
     return LevelDom.wrapMessageEvent(e);
   }
 
-  String get data() => _ptr.data;
+  String get data => _ptr.data;
 
-  String get lastEventId() => _ptr.lastEventId;
+  String get lastEventId => _ptr.lastEventId;
 
-  MessagePort get messagePort() => LevelDom.wrapMessagePort(_ptr.messagePort);
+  MessagePort get messagePort => LevelDom.wrapMessagePort(_ptr.messagePort);
 
-  String get origin() => _ptr.origin;
+  String get origin => _ptr.origin;
 
-  Window get source() => LevelDom.wrapWindow(_ptr.source);
+  Window get source => LevelDom.wrapWindow(_ptr.source);
 }