anchor.diff:  }
   
   /// Find changes between Lists [a] and [b] and apply this changes to Set [n].
  -void _updateSet(List a, List b, Set n) {
  +void updateClasses(List a, List b, Set n) {
     if (a != null && a.length > 0) {
       if (b == null || b.length == 0) {
         n.removeAll(a);
  
positive.code: }
  
  /// Find changes between maps [a] and [b] and apply this changes to map [n].
  void _updateMap(Map a, Map b, Map n) {
    if (a != null && a.length > 0) {
      if (b == null || b.length == 0) {
        // all keys removed
  
negative.code:       final html.Element r = ref;
  
        if (!identical(attrs, other.attrs)) {
          updateAttrs(attrs, other.attrs, r.attributes);
        }
  
        if (!identical(style, other.style)) {
          updateStyle(style, other.style, r.style);
        }
  
        if (!identical(classes, other.classes)) {
          updateClasses(classes, other.classes, r.classes);
        }
  
        if ((flags & componentFlag) != 0) {
  