Roll Observatory packages and add a roll script

packages/matcher/lib/src/interfaces.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.interfaces;
 
 // To decouple the reporting of errors, and allow for extensibility of
 // matchers, we make use of some interfaces.
 
 /// Matchers build up their error messages by appending to
@@ skipping 40 matching lines @@
   /// the [Map] that was passed to and supplemented by [matches]
   /// with additional information about the mismatch, and [mismatchDescription]
   /// is the [Description] that is being built to decribe the mismatch.
   /// A few matchers make use of the [verbose] flag to provide detailed
   /// information that is not typically included but can be of help in
   /// diagnosing failures, such as stack traces.
   Description describeMismatch(
       item, Description mismatchDescription, Map matchState, bool verbose) =>
       mismatchDescription;
 }