anchor.diff:    // See https://github.com/dart-lang/sdk/issues/41823.
     /// Whether http timeline logging is enabled.
     ValueListenable<bool> get httpTimelineLoggingEnabled =>
  -      _httpTimelineLoggingEnabledNotifier;
  -  final _httpTimelineLoggingEnabledNotifier = ValueNotifier<bool>(false);
  -
  -  // TODO(kenz): change these streams to ValueListenables or remove altogether
  -  // if we can refactor the FlutterFramesChart to be written with more idiomatic
  -  // Flutter.
  -
  -  /// Stream controller that notifies the timeline has been processed.
  -  Stream<bool> get onTimelineProcessed => _timelineProcessedController.stream;
  -  final _timelineProcessedController = StreamController<bool>.broadcast();
  -
  -  /// Stream controller that notifies that offline data was loaded into the
  -  /// timeline.
  -  ///
  -  /// Subscribers to this stream will be responsible for updating the UI for the
  -  /// new value of [timelineData].
  -  Stream<OfflineTimelineData> get onLoadOfflineData =>
  -      _loadOfflineDataController.stream;
  -  final _loadOfflineDataController =
  -      StreamController<OfflineTimelineData>.broadcast();
  -
  -  /// Stream controller that notifies the timeline screen when a non-fatal error
  -  /// should be logged for the timeline.
  -  final _nonFatalErrorController = StreamController<String>.broadcast();
  -
  -  Stream<String> get onNonFatalError => _nonFatalErrorController.stream;
  -
  -  /// Stream controller that notifies the timeline has been cleared.
  -  final _clearController = StreamController<bool>.broadcast();
  -
  -  Stream<bool> get onTimelineCleared => _clearController.stream;
  +      _httpTimelineLoggingEnabled;
  +  final _httpTimelineLoggingEnabled = ValueNotifier<bool>(false);
   
     // TODO(kenz): switch to use VmFlagManager-like pattern once
     // https://github.com/dart-lang/sdk/issues/41822 is fixed.
  
positive.code:     }
    }
  
    void logNonFatalError(String message) {
      _nonFatalErrorController.add(message);
    }
  
    @override
    void dispose() {
      cpuProfilerController.dispose();
      _selectedTimelineEventNotifier.dispose();
      _clearController.close();
      _loadOfflineDataController.close();
      _nonFatalErrorController.close();
    }
  }
  
negative.code:     _flutterFrames.value = [];
      _selectedTimelineEventNotifier.value = null;
      _selectedFrameNotifier.value = null;
      _processing.value = false;
    }
  
    void recordTrace(Map<String, dynamic> trace) {
  