Adding isNotEmpty property to collection and string.

sdk/lib/_internal/compiler/implementation/lib/js_string.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.
 
 part of _interceptors;
 
 /**
  * The interceptor class for [String]. The compiler recognizes this
  * class as an interceptor, and changes references to [:this:] to
  * actually use the receiver of the method, which is generated as an extra
@@ skipping 209 matching lines @@
     return stringLastIndexOfUnchecked(this, other, start);
   }
 
   bool contains(Pattern other, [int startIndex = 0]) {
     checkNull(other);
     return stringContainsUnchecked(this, other, startIndex);
   }
 
   bool get isEmpty => length == 0;
 
+  bool get isNotEmpty => !isEmpty;
+
   int compareTo(String other) {
     if (other is !String) throw new ArgumentError(other);
     return this == other ? 0
       : JS('bool', r'# < #', this, other) ? -1 : 1;
   }
 
   // Note: if you change this, also change the function [S].
   String toString() => this;
 
   /**
@@ skipping 32 matching lines @@
  */
 class _CodeUnits extends UnmodifiableListBase<int> {
   /** The string that this is the code units of. */
   String _string;
 
   _CodeUnits(this._string);
 
   int get length => _string.length;
   int operator[](int i) => _string.codeUnitAt(i);
 }