Only process each StyleSheetContents once when collecting features during style resolution

Source/core/css/resolver/ScopedStyleTree.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 16 matching lines @@
 #include "config.h"
 #include "core/css/resolver/ScopedStyleTree.h"
 
 #include "core/css/RuleFeature.h"
 #include "core/dom/Document.h"
 #include "core/dom/shadow/ElementShadow.h"
 #include "core/dom/shadow/ShadowRoot.h"
 
 namespace WebCore {
 
+class StyleSheetContents;
+
 ScopedStyleResolver* ScopedStyleTree::ensureScopedStyleResolver(ContainerNode& scopingNode)
 {
     bool isNewEntry;
     ScopedStyleResolver* scopedStyleResolver = addScopedStyleResolver(scopingNode, isNewEntry);
     if (isNewEntry)
         setupScopedStylesTree(scopedStyleResolver);
     return scopedStyleResolver;
 }
 
 ScopedStyleResolver* ScopedStyleTree::scopedStyleResolverFor(const ContainerNode& scopingNode)
@@ skipping 137 matching lines @@
     if (!cacheIsValid(&scopingNode))
         return;
 
     if (m_cache.scopedResolver && m_cache.scopedResolver->scopingNode() == scopingNode)
         m_cache.scopedResolver = m_cache.scopedResolver->parent();
     m_cache.nodeForScopedStyles = scopingNode.parentOrShadowHostNode();
 }
 
 void ScopedStyleTree::collectFeaturesTo(RuleFeatureSet& features)
 {
+    HashSet<const StyleSheetContents*> visitedSharedStyleSheetContents;
     for (HashMap<const ContainerNode*, OwnPtr<ScopedStyleResolver> >::iterator it = m_authorStyles.begin(); it != m_authorStyles.end(); ++it)
-        it->value->collectFeaturesTo(features);
+        it->value->collectFeaturesTo(features, visitedSharedStyleSheetContents);
 }
 
 inline void ScopedStyleTree::reparentNodes(const ScopedStyleResolver* oldParent, ScopedStyleResolver* newParent)
 {
     // FIXME: this takes O(N) (N = number of all scoping nodes).
     for (HashMap<const ContainerNode*, OwnPtr<ScopedStyleResolver> >::iterator it = m_authorStyles.begin(); it != m_authorStyles.end(); ++it) {
         if (it->value->parent() == oldParent)
             it->value->setParent(newParent);
     }
 }
 
 void ScopedStyleTree::remove(const ContainerNode* scopingNode)
 {
     if (!scopingNode || scopingNode->isDocumentNode())
         return;
 
     ScopedStyleResolver* resolverRemoved = lookupScopedStyleResolverFor(scopingNode);
     if (!resolverRemoved)
         return;
 
     reparentNodes(resolverRemoved, resolverRemoved->parent());
     if (m_cache.scopedResolver == resolverRemoved)
         m_cache.clear();
 
     m_authorStyles.remove(scopingNode);
 }
 
 } // namespace WebCore