Implement _UnorderedEquals in terms of _UnorderedMatches in pkg/unittest.

pkg/unittest/test/matchers_test.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.
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:unittest/unittest.dart';
 
 import 'test_utils.dart';
@@ skipping 463 matching lines @@
           "Expected: equals [1] unordered "
           "Actual: [1, 2] "
           "Which: has too many elements (2 > 1)");
       shouldFail(d, unorderedEquals([3, 2, 1]),
           "Expected: equals [3, 2, 1] unordered "
           "Actual: [1, 2] "
           "Which: has too few elements (2 < 3)");
       shouldFail(d, unorderedEquals([3, 1]),
           "Expected: equals [3, 1] unordered "
           "Actual: [1, 2] "
-          "Which: has no match for element <3> at index 0");
+          "Which: has no match for <3> at index 0");
     });
 
     test('unorderedMatchess', () {
       var d = [1, 2];
       shouldPass(d, unorderedMatches([2, 1]));
       shouldPass(d, unorderedMatches([greaterThan(1), greaterThan(0)]));
       shouldFail(d, unorderedMatches([greaterThan(0)]),
           "Expected: matches [a value greater than <0>] unordered "
           "Actual: [1, 2] "
           "Which: has too many elements (2 > 1)");
@@ skipping 284 matching lines @@
 
   X() {
     print(foo);
   }
 }
 
 abstract class Abstraction {
   void norealization();
 }