Make isEmpty a getter.

lib/coreimpl/linked_hash_map.dart

 // 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.
 
 /**
  * This class represents a pair of two objects, used by LinkedHashMap
  * to store a {key, value} in a list.
  */
 class KeyValuePair<K, V> {
   KeyValuePair(this.key, this.value) {}
@@ skipping 88 matching lines @@
   bool containsValue(V value) {
     return _list.some(bool _(KeyValuePair<K, V> entry) {
       return (entry.value == value);
     });
   }
 
   int get length {
     return _map.length;
   }
 
-  bool isEmpty() {
+  bool get isEmpty {
     return length == 0;
   }
 
   void clear() {
     _map.clear();
     _list.clear();
   }
 
   String toString() {
     return Maps.mapToString(this);
   }
 }