Get rid of a lot of () for getters.

lib/html/src/BeforeLoadEventWrappingImplementation.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 BeforeLoadEventWrappingImplementation extends EventWrappingImplementation implements BeforeLoadEvent {
   BeforeLoadEventWrappingImplementation._wrap(ptr) : super._wrap(ptr);
 
   factory BeforeLoadEventWrappingImplementation(String type, String url,
       [bool canBubble = true, bool cancelable = true]) {
     final e = dom.document.createEvent("BeforeLoadEvent");
     e.initBeforeLoadEvent(type, canBubble, cancelable, url);
     return LevelDom.wrapBeforeLoadEvent(e);
   }
 
-  String get url() => _ptr.url;
+  String get url => _ptr.url;
 }