anchor.diff:    })  : _scheduler = scheduler,
           _resourceProvider = resourceProvider,
           _byteStore = byteStore,
  -        _contentOverlay = contentOverlay ?? FileContentOverlay(),
  +        _contentOverlay = FileContentOverlay(),
           _analysisOptions = analysisOptions,
           enableIndex = enableIndex,
           _logger = logger,
  
positive.code:     required PerformanceLog logger,
      required ResourceProvider resourceProvider,
      required ByteStore byteStore,
      @Deprecated('Use OverlayResourceProvider instead')
          FileContentOverlay? contentOverlay,
      required SourceFactory sourceFactory,
      required AnalysisOptionsImpl analysisOptions,
      required Packages packages,
  
negative.code:     PerformanceLog logger,
      ResourceProvider resourceProvider,
      ByteStore byteStore,
      // ignore: avoid_unused_constructor_parameters
      FileContentOverlay? contentOverlay,
      // ignore: avoid_unused_constructor_parameters
      ContextRoot? contextRoot,
  