Adding isNotEmpty property to collection and string.

runtime/lib/growable_array.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.
 
 class _GrowableObjectArray<T> implements List<T> {
   static final int _classId = (new _GrowableObjectArray(0))._cid;
 
   void insert(int index, T element) {
     if (index < 0 || index > length) {
       throw new RangeError.range(index, 0, length);
@@ skipping 306 matching lines @@
   }
 
   T elementAt(int index) {
     return this[index];
   }
 
   bool get isEmpty {
     return this.length == 0;
   }
 
+  bool get isNotEmpty => !isEmpty;
+
   void clear() {
     this.length = 0;
   }
 
   Iterable<T> get reversed => IterableMixinWorkaround.reversedList(this);
 
   void sort([int compare(T a, T b)]) {
     IterableMixinWorkaround.sortList(this, compare);
   }
 
@@ skipping 10 matching lines @@
   }
 
   Set<T> toSet() {
     return new Set<T>.from(this);
   }
 
   Map<int, T> asMap() {
     return IterableMixinWorkaround.asMapList(this);
   }
 }