Make isEmpty a getter.

samples/ui_lib/observable/ChangeEvent.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.
 
 /** A change to an observable instance. */
 class ChangeEvent {
   // TODO(sigmund): capture language issues around enums & create a cannonical
   // Dart enum design.
   /** Type denoting an in-place update event. */
   static const UPDATE = 0;
@@ skipping 54 matching lines @@
   List<ChangeEvent> events;
 
   EventSummary(this.target) : events = new List<ChangeEvent>();
 
   void addEvent(ChangeEvent e) {
     events.add(e);
   }
 
   /** Notify listeners of [target] and parents of [target] about all changes. */
   void notify() {
-    if (!events.isEmpty()) {
+    if (!events.isEmpty) {
       for (Observable obj = target; obj != null; obj = obj.parent) {
         for (final listener in obj.listeners) {
           listener(this);
         }
       }
     }
   }
 }
 
 /** A listener of change events. */
 typedef void ChangeListener(EventSummary events);