Get rid of a lot of () for getters.

lib/html/src/DataAttributeMap.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.
 
 /**
  * Provides a Map abstraction on top of data-* attributes, similar to the
  * dataSet in the old DOM.
  */
 class _DataAttributeMap implements AttributeMap {
 
@@ skipping 51 matching lines @@
   Collection<String> getValues() {
     final values = new List<String>();
     _attributes.forEach((String key, String value) {
       if (_matches(key)) {
         values.add(value);
       }
     });
     return values;
   }
 
-  int get length() => getKeys().length;
+  int get length => getKeys().length;
 
   // TODO: Use lazy iterator when it is available on Map.
   bool isEmpty() => length == 0;
 
   // Helpers.
   String _attr(String key) => 'data-$key';
   bool _matches(String key) => key.startsWith('data-');
   String _strip(String key) => key.substring(5);
 }