Implement more fixes.

pkg/analysis_services/lib/src/correction/source_buffer.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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library services.src.correction.source_buffer;
 
 import 'package:analysis_services/correction/change.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 
 /**
  * Helper for building Dart source with linked positions.
  */
 class SourceBuilder {
   final String file;
   final int offset;
   final StringBuffer _buffer = new StringBuffer();
 
   final List<LinkedPositionGroup> linkedPositionGroups = <LinkedPositionGroup>[
       ];
   LinkedPositionGroup _currentLinkedPositionGroup;
   int _currentPositionStart;
 
   SourceBuilder(this.file, this.offset);
 
+  SourceBuilder.buffer() : file = null, offset = 0;
+
+  int get length => _buffer.length;
+
   void addProposal(String proposal) {
     // TODO(scheglov) implement
 //    _currentPositionGroup.addProposal();
   }
 
   void addProposals(List<String> proposals) {
     proposals.forEach((proposal) => addProposal(proposal));
   }
 
   /**
@@ skipping 37 matching lines @@
   /**
    * Adds position location [SourceRange] using current fields.
    */
   void _addPosition() {
     int start = offset + _currentPositionStart;
     int end = offset + _buffer.length;
     Position position = new Position(file, start, end - start);
     _currentLinkedPositionGroup.add(position);
   }
 }