pkg/matcher: test cleanup

pkg/matcher/test/test_common.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.
 
-library test_common;
+library matcher.test_common;
 
 import 'dart:collection';
 
 import 'package:matcher/matcher.dart';
 
 class Widget {
   int price;
 }
 
 class HasPrice extends CustomMatcher {
@@ skipping 34 matching lines @@
       _count--;
       return true;
     }
     _current = null;
     return false;
   }
 
   get current => _current;
 }