Add "last" setter to List.

samples-dev/swarm/swarm_ui_lib/observable/observable.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.
 
 library observable;
 
 part 'ChangeEvent.dart';
 part 'EventBatch.dart';
 
 /**
@@ skipping 127 matching lines @@
   ObservableList([Observable parent = null])
     : super(parent), _internal = new List<T>();
 
   T operator [](int index) => _internal[index];
 
   void operator []=(int index, T value) {
     recordListUpdate(index, value, _internal[index]);
     _internal[index] = value;
   }
 
+  void set last(T value) {
+    if (length == 0) throw new StateError("No element");
+    int index = length - 1;
+    recordListUpdate(index, value, _internal[index]);
+    _internal[index] = value;
+  }
+
   int get length => _internal.length;
 
   void set length(int value) {
     _internal.length = value;
     recordGlobalChange();
   }
 
   void clear() {
     _internal.clear();
     recordGlobalChange();
@@ skipping 196 matching lines @@
     // Only fire on an actual change.
     if (!identical(newValue, _value)) {
       final oldValue = _value;
       _value = newValue;
       recordPropertyUpdate("value", newValue, oldValue);
     }
   }
 
   T _value;
 }