pkg/matcher: refactored code around data-structure vs execution-based matchers

pkg/matcher/lib/src/map_matchers.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 matcher.map_matchers;
 
-import 'expect.dart';
 import 'interfaces.dart';
+import 'util.dart';
 
 /// Returns a matcher which matches maps containing the given [value].
 Matcher containsValue(value) => new _ContainsValue(value);
 
 class _ContainsValue extends Matcher {
   final _value;
 
   const _ContainsValue(this._value);
 
   bool matches(item, Map matchState) => item.containsValue(_value);
@@ skipping 28 matching lines @@
           .addDescriptionOf(_key);
     } else {
       mismatchDescription.add(' contains key ').addDescriptionOf(_key).
           add(' but with value ');
       _valueMatcher.describeMismatch(item[_key], mismatchDescription,
           matchState, verbose);
       return mismatchDescription;
     }
   }
 }