anchor.diff:          } else if (_isHost(selector)) {
             // Replace :host with host class.
             compoundSelector._sequences[j] =
  -              _createClassSelectorSequence(hostClass);
  +              _createClassSelectorSequence(_hostClass);
           }
         }
       }
     }
   
  +  @override
     void visitSelectorGroup(SelectorGroup node) {
       var complexSelectors = <_ComplexSelector>[];
       for (var selector in node.selectors) {
  
positive.code:     }
    }
  
    void shimSelectors(_ComplexSelector selector) {
      // Remove all ::content and ::shadow selectors. This does not correctly
      // emulate the behavior of these selectors, however, the shim never has
  
negative.code:         : false);
    }
  
    void _shimPolyfillUnscopedRule(RuleSet ruleSet) {
      if (_matchesElement(ruleSet.selectorGroup, 'polyfill-unscoped-rule')) {
        var contentSelectorGroup = _selectorGroupForProperty(
            ruleSet.declarationGroup, 'content',
  