Adding isNotEmpty property to collection and string.

sdk/lib/collection/linked_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;
 
 class LinkedHashSet<E> extends _HashSetBase<E> {
 
   external LinkedHashSet();
 
   factory LinkedHashSet.from(Iterable<E> iterable) {
     return new LinkedHashSet<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);
 
   external void forEach(void action(E element));
 
   external E get first;
 
   external E get last;
 
   E get single {
     if (length == 1) return first;
@@ skipping 12 matching lines @@
 
   external void removeWhere(bool test(E element));
 
   external void retainWhere(bool test(E element));
 
   external void clear();
 
   // Set.
   Set<E> _newSet() => new LinkedHashSet<E>();
 }