Roll Observatory packages and add a roll script

packages/dart_style/lib/src/argument_list_visitor.dart

 // Copyright (c) 2014, 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 dart_style.src.argument_list_visitor;
 
 import 'package:analyzer/analyzer.dart';
 
 import 'chunk.dart';
 import 'rule/argument.dart';
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   static bool _isCollectionArgument(Expression expression) {
     if (expression is NamedExpression) {
       expression = (expression as NamedExpression).expression;
     }
 
     // TODO(rnystrom): Should we step into parenthesized expressions?
 
     return expression is ListLiteral || expression is MapLiteral;
   }
 }