Avoid style sharing with mis-matched descendant selectors

Source/core/css/resolver/StyleResolver.cpp

Index: Source/core/css/resolver/StyleResolver.cpp
diff --git a/Source/core/css/resolver/StyleResolver.cpp b/Source/core/css/resolver/StyleResolver.cpp
index 84ca02401779ee2153e0c113180e7206415665d3..9f27cf9878bd8ea6619a5f66d384cb519c2159e3 100644
--- a/Source/core/css/resolver/StyleResolver.cpp
+++ b/Source/core/css/resolver/StyleResolver.cpp
@@ -267,6 +267,7 @@ void StyleResolver::collectFeatures()
     m_styleTree.collectFeaturesTo(m_features);
 
     m_siblingRuleSet = makeRuleSet(m_features.siblingRules);
+    m_descendantRuleSet = makeRuleSet(m_features.descendantRules);
     m_uncommonAttributeRuleSet = makeRuleSet(m_features.uncommonAttributeRules);
 }
 
@@ -612,7 +613,7 @@ PassRefPtr<RenderStyle> StyleResolver::styleForElement(Element* element, RenderS
     StyleResolverState state(document(), element, defaultParent, regionForStyling);
 
     if (sharingBehavior == AllowStyleSharing && !state.distributedToInsertionPoint() && state.parentStyle()) {
-        SharedStyleFinder styleFinder(m_features, m_siblingRuleSet.get(), m_uncommonAttributeRuleSet.get(), this);
+        SharedStyleFinder styleFinder(m_features, m_siblingRuleSet.get(), m_uncommonAttributeRuleSet.get(), m_descendantRuleSet.get(), this);
         RefPtr<RenderStyle> sharedStyle = styleFinder.locateSharedStyle(state.elementContext());
         if (sharedStyle)
             return sharedStyle.release();