Don't add rule feature data for rules which may never match.

third_party/WebKit/Source/core/css/RuleFeature.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 41 matching lines @@
 
 class CORE_EXPORT RuleFeatureSet {
     DISALLOW_NEW();
 public:
     RuleFeatureSet();
     ~RuleFeatureSet();
 
     void add(const RuleFeatureSet&);
     void clear();
 
-    void collectFeaturesFromRuleData(const RuleData&);
+    enum SelectorPreMatch { SelectorNeverMatches, SelectorMayMatch };
+
+    SelectorPreMatch collectFeaturesFromRuleData(const RuleData&);
 
     bool usesSiblingRules() const { return !siblingRules.isEmpty(); }
     bool usesFirstLineRules() const { return m_metadata.usesFirstLineRules; }
     bool usesWindowInactiveSelector() const { return m_metadata.usesWindowInactiveSelector; }
 
     unsigned maxDirectAdjacentSelectors() const { return m_metadata.maxDirectAdjacentSelectors; }
 
     bool hasSelectorForAttribute(const AtomicString& attributeName) const
     {
         ASSERT(!attributeName.isEmpty());
@@ skipping 38 matching lines @@
         void add(const FeatureMetadata& other);
         void clear();
 
         bool usesFirstLineRules = false;
         bool usesWindowInactiveSelector = false;
         bool foundSiblingSelector = false;
         bool foundInsertionPointCrossing = false;
         unsigned maxDirectAdjacentSelectors = 0;
     };
 
-    void collectFeaturesFromSelector(const CSSSelector&, FeatureMetadata&);
+    SelectorPreMatch collectFeaturesFromSelector(const CSSSelector&, FeatureMetadata&);
 
     InvalidationSet& ensureClassInvalidationSet(const AtomicString& className, InvalidationType);
     InvalidationSet& ensureAttributeInvalidationSet(const AtomicString& attributeName, InvalidationType);
     InvalidationSet& ensureIdInvalidationSet(const AtomicString& id, InvalidationType);
     InvalidationSet& ensurePseudoInvalidationSet(CSSSelector::PseudoType, InvalidationType);
 
     void updateInvalidationSets(const RuleData&);
     void updateInvalidationSetsForContentAttribute(const RuleData&);
 
     struct InvalidationSetFeatures {
@@ skipping 32 matching lines @@
     PseudoTypeInvalidationSetMap m_pseudoInvalidationSets;
 
     friend class RuleFeatureSetTest;
 };
 
 } // namespace blink
 
 WTF_ALLOW_MOVE_AND_INIT_WITH_MEM_FUNCTIONS(blink::RuleFeature);
 
 #endif // RuleFeature_h