anchor.diff:    }
   
     /**
  +   * Return the unlinked bundle of [file] for the current file state, or `null`.
  +   */
  +  PackageBundle _getCurrentUnlinked(_File file) {
  +    String key = '${file.currentContentHash}.unlinked';
  +    List<int> bytes = _byteStore.get(key);
  +    return bytes != null ? new PackageBundle.fromBuffer(bytes) : null;
  +  }
  +
  +  /**
      * TODO(scheglov) It would be nice to get URIs of "parts" from unlinked.
      */
     _ReferencedUris _getReferencedUris(_File file) {
  
positive.code:    * [changeFile] invocation.
     */
    void changeFile(String path) {
      // TODO(scheglov) Don't clear, schedule API signature validation.
      _fileContentHashMap.clear();
      _dependencySignatureMap.clear();
      _filesToAnalyze.add(path);
      _filesToAnalyze.addAll(_explicitFiles);
      // TODO(scheglov) name?!
      _hasWorkStreamController.add('do it!');
    }
  
  
negative.code:   final _explicitFiles = new LinkedHashSet<String>();
  
    /**
     * The set of files were reported as changed through [changeFile] and for
     * which API signatures should be recomputed and compared before performing
     * any other analysis.
     */
    final _filesToVerifyUnlinkedSignature = new Set<String>();
  
    /**
     * The set of files that are currently scheduled for analysis.
     */
    final _filesToAnalyze = new LinkedHashSet<String>();
  