Adding isNotEmpty property to collection and string.

sdk/lib/collection/hash_set.dart

 // Copyright (c) 2013, 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.
 
 part of dart.collection;
 
 /** Common parts of [HashSet] and [LinkedHashSet] implementations. */
 abstract class _HashSetBase<E> extends IterableBase<E> implements Set<E> {
   // Set.
   bool containsAll(Iterable<E> other) {
@@ skipping 52 matching lines @@
     return new HashSet<E>()..addAll(iterable);
   }
 
   // Iterable.
   external Iterator<E> get iterator;
 
   external int get length;
 
   external bool get isEmpty;
 
+  external bool get isNotEmpty;
+
   external bool contains(Object object);
 
   // Collection.
   external void add(E element);
 
   external void addAll(Iterable<E> objects);
 
   external bool remove(Object object);
 
   external void removeAll(Iterable objectsToRemove);
 
   external void removeWhere(bool test(E element));
 
   external void retainWhere(bool test(E element));
 
   external void clear();
 
   // Set.
   Set<E> _newSet() => new HashSet<E>();
 }