anchor.diff:     * immediately.
      */
     Future<Null> waitForIdle() => _statusSupport.waitForIdle();
  -
  -  /**
  -   * Add the given [driver] and schedule it to perform its work.
  -   */
  -  void add(AnalysisDriverGeneric driver) {
  -    _drivers.add(driver);
  -    _hasWork.notify();
  -  }
   
     /**
      * Remove the given [driver] from the scheduler, so that it will not be
  
positive.code:     return completer.future;
    }
  
    /**
     * Return a [Future] that completes with a [AnalysisResult] for the Dart
     * file with the given [path]. If the file is not a Dart file or cannot
  
negative.code:       }
      }
      return null;
    }
  
    void _reportException(String path, exception, StackTrace stackTrace) {
  