Fix ResynthesizerResultProvider's handling of parts.

pkg/analyzer/lib/src/task/html.dart

 // Copyright (c) 2015, 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.src.task.html;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/dart/scanner/scanner.dart';
@@ skipping 56 matching lines @@
   @override
   String get encoding => source.encoding;
 
   @override
   String get fullName => source.fullName;
 
   @override
   bool get isInSystemLibrary => source.isInSystemLibrary;
 
   @override
+  Source get librarySource => source;
+
+  @override
   int get modificationStamp => source.modificationStamp;
 
   @override
   String get shortName => source.shortName;
 
   @override
   Uri get uri => source.uri
       .replace(queryParameters: {'offset': fragments[0].offset.toString()});
 
   @override
@@ skipping 325 matching lines @@
    * The content of the fragment.
    */
   final String content;
 
   /**
    * Initialize a newly created script fragment to have the given [offset] and
    * [content].
    */
   ScriptFragment(this.offset, this.line, this.column, this.content);
 }