Avoid style sharing with mis-matched descendant selectors

Source/core/css/resolver/SharedStyleFinder.h

Index: Source/core/css/resolver/SharedStyleFinder.h
diff --git a/Source/core/css/resolver/SharedStyleFinder.h b/Source/core/css/resolver/SharedStyleFinder.h
index 1e123750427cb2c4363bbed0367440a3de2119ff..47e4d9f26a13919bc21eb9aab9120bc6eef6bdd7 100644
--- a/Source/core/css/resolver/SharedStyleFinder.h
+++ b/Source/core/css/resolver/SharedStyleFinder.h
@@ -38,11 +38,12 @@ public:
     // RuleSets are passed non-const as the act of matching against them can cause them
     // to be compacted. :(
     SharedStyleFinder(const RuleFeatureSet& features, RuleSet* siblingRuleSet,
-        RuleSet* uncommonAttributeRuleSet, StyleResolver* styleResolver)
+        RuleSet* uncommonAttributeRuleSet, RuleSet* descendantRuleSet, StyleResolver* styleResolver)
         : m_elementAffectedByClassRules(false)
         , m_features(features)
         , m_siblingRuleSet(siblingRuleSet)
         , m_uncommonAttributeRuleSet(uncommonAttributeRuleSet)
+        , m_descendantRuleSet(descendantRuleSet)
         , m_styleResolver(styleResolver)
     { }
 
@@ -61,11 +62,13 @@ private:
     bool canShareStyleWithControl(const ElementResolveContext&, Element*) const;
     bool sharingCandidateHasIdenticalStyleAffectingAttributes(const ElementResolveContext&, Element*) const;
     bool matchesRuleSet(const ElementResolveContext&, RuleSet*);
+    bool candidateMatchesDescendantRules(const ElementResolveContext&, Element*) const;
 
     bool m_elementAffectedByClassRules;
     const RuleFeatureSet& m_features;
     RuleSet* m_siblingRuleSet;
     RuleSet* m_uncommonAttributeRuleSet;
+    RuleSet* m_descendantRuleSet;
     StyleResolver* m_styleResolver;
 };