anchor.diff:     * Buffer containing strings printed by the analysis server.
      */
     List<String> _printBuffer;
  +
  +  /**
  +   * Contents of overlay files.
  +   */
  +  final Map<int, String> _overlayContents = <int, String>{};
   
     /**
      * Initialize a newly created handler for GET requests.
  
positive.code:       _returnCacheEntry(request);
      } else if (path == COMPLETION_PATH) {
        _returnCompletionInfo(request);
      } else if (path == OVERLAYS_PATH) {
        _returnOverlaysInfo(request);
      } else {
  
negative.code:   static const String COMPLETION_PATH = '/completion';
  
    /**
     * The path used to request an overlay contents.
     */
    static const String OVERLAY_PATH = '/overlay';
  
    /**
     * The path used to request overlays information.
     */
    static const String OVERLAYS_PATH = '/overlays';
  