Avoid style sharing with mis-matched descendant selectors

Source/core/css/resolver/StyleResolver.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 249 matching lines @@
     return ruleSet.release();
 }
 
 void StyleResolver::collectFeatures()
 {
     m_features.clear();
     m_ruleSets.collectFeaturesTo(m_features, document().isViewSource());
     m_styleTree.collectFeaturesTo(m_features);
 
     m_siblingRuleSet = makeRuleSet(m_features.siblingRules);
+    m_descendantRuleSet = makeRuleSet(m_features.descendantRules);
     m_uncommonAttributeRuleSet = makeRuleSet(m_features.uncommonAttributeRules);
 }
 
 bool StyleResolver::hasRulesForId(const AtomicString& id) const
 {
     return m_features.idsInRules.contains(id.impl());
 }
 
 void StyleResolver::addToStyleSharingList(Element* element)
 {
@@ skipping 325 matching lines @@
         }
         element->document().setHasNodesWithPlaceholderStyle();
         return s_styleNotYetAvailable;
     }
 
     if (element == document().documentElement())
         resetDirectionAndWritingModeOnDocument(document());
     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();
     }
 
     if (state.parentStyle()) {
         state.setStyle(RenderStyle::create());
         state.style()->inheritFrom(state.parentStyle(), isAtShadowBoundary(element) ? RenderStyle::AtShadowBoundary : RenderStyle::NotAtShadowBoundary);
     } else {
         state.setStyle(defaultStyleForElement());
@@ skipping 971 matching lines @@
         m_matchedPropertiesSearches, m_matchedPropertiesHit, m_matchedPropertiesSharedInheritedHit, m_matchedPropertiesToCache, m_matchedPropertiesEnteredIntoCache);
 
     fprintf(stderr, "Total:\n");
     printStyleStats(m_totalSearches, m_totalElementsEligibleForSharing, m_totalStylesShared, m_totalSearchFoundSiblingForSharing, m_totalSearchesMissedSharing,
         m_totalMatchedPropertiesSearches, m_totalMatchedPropertiesHit, m_totalMatchedPropertiesSharedInheritedHit, m_totalMatchedPropertiesToCache, m_totalMatchedPropertiesEnteredIntoCache);
     fprintf(stderr, "--------------------------------------------------------------------------------\n");
 }
 #endif
 
 } // namespace WebCore