Roll Observatory packages and add a roll script

packages/dart_style/lib/src/formatter_options.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.formatter_options;
 
 import 'dart:convert';
 import 'dart:io';
 
 import 'source_code.dart';
@@ skipping 99 matching lines @@
 class _OverwriteReporter extends _PrintReporter {
   void showFile(File file, String label, SourceCode output, {bool changed}) {
     if (changed) {
       file.writeAsStringSync(output.text);
       print("Formatted $label");
     } else {
       print("Unchanged $label");
     }
   }
 }