Factor the style invalidation tree walk out of RuleFeatureSet, and make it generic.

Source/core/css/RuleFeature.h

Index: Source/core/css/RuleFeature.h
diff --git a/Source/core/css/RuleFeature.h b/Source/core/css/RuleFeature.h
index df44c3e2fc49b04c6b0b1c033a040df05c777998..c27fcdfdc249aef4242e6997e5666788ffc485a0 100644
--- a/Source/core/css/RuleFeature.h
+++ b/Source/core/css/RuleFeature.h
@@ -76,7 +76,6 @@ public:
     {
         ASSERT(!classValue.isEmpty());
         return m_classInvalidationSets.get(classValue);
-
     }
 
     inline bool hasSelectorForId(const AtomicString& idValue) const
@@ -140,9 +139,6 @@ private:
 
     void addClassToInvalidationSet(const AtomicString& className, Element*);
 
-    bool invalidateStyleForClassChange(Element*, Vector<AtomicString>&, bool foundInvalidationSet);
-    bool invalidateStyleForClassChangeOnChildren(Element*, Vector<AtomicString>& invalidationClasses, bool foundInvalidationSet);
-
     InvalidationList& ensurePendingInvalidationList(Element*);
 
     FeatureMetadata m_metadata;
@@ -150,8 +146,11 @@ private:
     PendingInvalidationMap m_pendingInvalidationMap;
 
     bool m_targetedStyleRecalcEnabled;
+
+    friend class StyleInvalidationTreeWalk;
 };
 
+
 } // namespace WebCore
 
 #endif // RuleFeature_h