Roll Observatory packages and add a roll script

packages/analyzer/lib/analyzer.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 analyzer;
 
 import 'dart:io';
 
 import 'package:path/path.dart' as pathos;
 
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   /// The group of errors collected.
   AnalyzerErrorGroup get group =>
       new AnalyzerErrorGroup.fromAnalysisErrors(_errors);
 
   /// Whether any errors where collected.
   bool get hasErrors => !_errors.isEmpty;
 
   void onError(AnalysisError error) => _errors.add(error);
 }