Roll Observatory packages and add a roll script

packages/observe/lib/src/dirty_check.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.
 
 /// *Warning*: this library is **internal**, and APIs are subject to change.
 ///
 /// Tracks observable objects for dirty checking and testing purposes.
 ///
 /// It can collect all observed objects, which can be used to trigger
 /// predictable delivery of all pending changes in a test, including objects
@@ skipping 113 matching lines @@
   return new ZoneSpecification(
       registerCallback: wrapCallback,
       registerUnaryCallback: wrapUnaryCallback);
 }
 
 /// Forks a [Zone] off the current one that does dirty-checking automatically
 /// after each batch of async operations. Equivalent to:
 ///
 ///     Zone.current.fork(specification: dirtyCheckZoneSpec());
 Zone dirtyCheckZone() => Zone.current.fork(specification: dirtyCheckZoneSpec());