Roll Observatory packages and add a roll script

packages/unittest/lib/src/matcher/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 unittest.matcher.map_matchers;
 
 import 'interfaces.dart';
 import 'util.dart';
 
 /// Returns a matcher which matches maps containing the given [value].
@@ skipping 41 matching lines @@
       mismatchDescription
           .add(' contains key ')
           .addDescriptionOf(_key)
           .add(' but with value ');
       _valueMatcher.describeMismatch(
           item[_key], mismatchDescription, matchState, verbose);
       return mismatchDescription;
     }
   }
 }