Use the HashSet of attribute names in SharedStyleFinder.

sky/engine/core/css/resolver/StyleResolver.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 216 matching lines @@
     OwnPtr<MediaQueryEvaluator> m_medium;
     MediaQueryResultList m_viewportDependentMediaQueryResults;
 
     RawPtr<Document> m_document;
 
     ListHashSet<RawPtr<CSSStyleSheet>, 16> m_pendingStyleSheets;
 
     // FIXME: The entire logic of collecting features on StyleResolver, as well as transferring them
     // between various parts of machinery smells wrong. This needs to be better somehow.
     RuleFeatureSet m_features;
-    OwnPtr<RuleSet> m_attributeRuleSet;
 
     bool m_needCollectFeatures;
     bool m_printMediaType;
 
     StyleResourceLoader m_styleResourceLoader;
 
     unsigned m_styleSharingDepth;
     Vector<OwnPtr<StyleSharingList>, styleSharingMaxDepth> m_styleSharingLists;
 
     OwnPtr<StyleResolverStats> m_styleResolverStats;
     OwnPtr<StyleResolverStats> m_styleResolverStatsTotals;
     unsigned m_styleResolverStatsSequence;
 
     // Use only for Internals::updateStyleAndReturnAffectedElementCount.
     unsigned m_accessCount;
 };
 
 } // namespace blink
 
 #endif  // SKY_ENGINE_CORE_CSS_RESOLVER_STYLERESOLVER_H_