anchor.diff:        : super(resourceProvider);
   
     void addContext(Folder folder, File pubspecFile) {
  -    PubFolder pubFolder = new PubFolder(analysisServer.defaultSdk, folder, pubspecFile);
  -    analysisServer.folderMap[folder] = pubFolder;
  -    analysisServer.addContextToWorkQueue(pubFolder.context);
  +    ContextDirectory contextDirectory = new ContextDirectory(
  +        analysisServer.defaultSdk, folder, pubspecFile);
  +    analysisServer.folderMap[folder] = contextDirectory;
  +    analysisServer.addContextToWorkQueue(contextDirectory.context);
     }
   
     void applyChangesToContext(Folder contextFolder, ChangeSet changeSet) {
  
positive.code:   DartSdk defaultSdk = SHARED_SDK;
  
    /**
     * A table mapping [Folder]s to the [PubFolder]s associated with them.
     */
    final Map<Folder, PubFolder> folderMap = <Folder, PubFolder>{};
  
    /**
     * The context identifier used in the last status notification.
  
negative.code:    */
    AnalysisContext _context;
  
    ContextDirectory(DartSdk sdk, this._folder, this._pubspecFile) {
      // create AnalysisContext
      _context = AnalysisEngine.instance.createAnalysisContext();
      // TODO(scheglov) replace FileUriResolver with an Resource based resolver
  