Adding isNotEmpty property to collection and string.

sdk/lib/collection/list.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;
 
 /**
  * Abstract implementation of a list.
  *
  * All operations are defined in terms of `length`, `operator[]`,
@@ skipping 27 matching lines @@
     for (int i = 0; i < length; i++) {
       action(this[i]);
       if (length != this.length) {
         throw new ConcurrentModificationError(this);
       }
     }
   }
 
   bool get isEmpty => length == 0;
 
+  bool get isNotEmpty => !isEmpty;
+
   E get first {
     if (length == 0) throw new StateError("No elements");
     return this[0];
   }
 
   E get last {
     if (length == 0) throw new StateError("No elements");
     return this[length - 1];
   }
 
@@ skipping 412 matching lines @@
       for (E element in iterable) {
         this[index++] = element;
       }
     }
   }
 
   Iterable<E> get reversed => new ReversedListIterable(this);
 
   String toString() => ToString.iterableToString(this);
 }