anchor.diff:  
   /// Stores `styles: [ ... ]`,  `styleUrls: [ ... ]` for a given `@Component`.
   class ComponentStyles {
  -  /// All component `<style>` tags currently in the DOM.
  -  ///
  -  /// Intentionally stored as [Node] (which is sufficient for this use case) to
  -  /// avoid cost of reifying another type (the framework stores lists of [Node]
  -  /// elsewhere, but not [StyleElement]).
  -  static List<Node> _debugStyleElements;
  -
     /// Callbacks to invoke when [_debugClear] is called.
     static List<void Function()> _debugClearCallbacks;
   
  
positive.code:       }
        _debugClearCallbacks.clear();
      }
      if (_debugStyleElements != null) {
        for (final element in _debugStyleElements) {
          element.remove();
        }
        _debugStyleElements.clear();
      }
    }
  
    /// Registers a [callback] to be called by [_debugClear].
    ///
    /// Used to clear static component styles in generated views.
    static void debugOnClear(void Function() callback) {
      _debugClearCallbacks ??= [];
      _debugClearCallbacks.add(callback);
  
negative.code:     }
      final styles = _flattenStyles(_styles, target, _componentId).join();
      final styleElement = StyleElement()..text = styles;
      if (isDevMode) {
        // Remove style element from the DOM on hot restart.
        debugOnClear(() {
          styleElement.remove();
        });
      }
      document.head.append(styleElement);
    }
  