Roll Observatory packages and add a roll script

packages/observe/lib/src/observable_map.dart

 // Copyright (c) 2013, 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 observe.src.observable_map;
 
 import 'dart:collection';
 import 'package:observe/observe.dart';
 
 
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   // But this should fix "keys" and "values" in templates with minimal overhead.
   void _notifyKeysValuesChanged() {
     notifyChange(new PropertyChangeRecord(this, #keys, null, null));
     _notifyValuesChanged();
   }
 
   void _notifyValuesChanged() {
     notifyChange(new PropertyChangeRecord(this, #values, null, null));
   }
 }