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

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

Index: third_party/WebKit/Source/core/css/CSSSelector.h
diff --git a/third_party/WebKit/Source/core/css/CSSSelector.h b/third_party/WebKit/Source/core/css/CSSSelector.h
index 8a9e0904812b40859f2b31c6a75b8c029e5967fc..7517f5b6b159c82a6f46ee1eee8cb3864a2a0190 100644
--- a/third_party/WebKit/Source/core/css/CSSSelector.h
+++ b/third_party/WebKit/Source/core/css/CSSSelector.h
@@ -253,7 +253,6 @@ public:
 
     bool isAdjacentSelector() const { return m_relation == DirectAdjacent || m_relation == IndirectAdjacent; }
     bool isShadowSelector() const { return m_relation == ShadowPseudo || m_relation == ShadowDeep; }
-    bool isSiblingPseudo() const;
     bool isAttributeSelector() const { return m_match >= FirstAttributeSelectorMatch; }
     bool isHostPseudoClass() const { return m_pseudoType == PseudoHost || m_pseudoType == PseudoHostContext; }
     bool isInsertionPointCrossing() const { return m_pseudoType == PseudoHostContext || m_pseudoType == PseudoContent || m_pseudoType == PseudoSlotted; }
@@ -365,22 +364,6 @@ inline CSSSelector::AttributeMatchType CSSSelector::attributeMatchType() const
     return m_data.m_rareData->m_bits.m_attributeMatchType;
 }
 
-inline bool CSSSelector::isSiblingPseudo() const
-{
-    PseudoType type = pseudoType();
-    return type == PseudoEmpty
-        || type == PseudoFirstChild
-        || type == PseudoFirstOfType
-        || type == PseudoLastChild
-        || type == PseudoLastOfType
-        || type == PseudoOnlyChild
-        || type == PseudoOnlyOfType
-        || type == PseudoNthChild
-        || type == PseudoNthOfType
-        || type == PseudoNthLastChild
-        || type == PseudoNthLastOfType;
-}
-
 inline bool CSSSelector::isASCIILower(const AtomicString& value)
 {
     for (size_t i = 0; i < value.length(); ++i) {