Use SubSelector as relation on left-most selector

Source/core/css/RuleSet.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 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 39 matching lines @@
 using namespace HTMLNames;
 
 // -----------------------------------------------------------------
 
 static inline bool isSelectorMatchingHTMLBasedOnRuleHash(const CSSSelector& selector)
 {
     if (selector.match() == CSSSelector::Tag) {
         const AtomicString& selectorNamespace = selector.tagQName().namespaceURI();
         if (selectorNamespace != starAtom && selectorNamespace != xhtmlNamespaceURI)
             return false;
-        if (selector.relation() == CSSSelector::SubSelector) {
-            ASSERT(selector.tagHistory());
+        if (selector.relation() == CSSSelector::SubSelector && selector.tagHistory())
             return isSelectorMatchingHTMLBasedOnRuleHash(*selector.tagHistory());
-        }
         return true;
     }
     if (SelectorChecker::isCommonPseudoClassSelector(selector))
         return true;
     return selector.match() == CSSSelector::Id || selector.match() == CSSSelector::Class;
 }
 
 static inline bool selectorListContainsUncommonAttributeSelector(const CSSSelector* selector)
 {
     const CSSSelectorList* selectorList = selector->selectorList();
@@ skipping 100 matching lines @@
     AtomicString id;
     AtomicString className;
     AtomicString customPseudoElementName;
     AtomicString tagName;
 
 #ifndef NDEBUG
     m_allRules.append(ruleData);
 #endif
 
     const CSSSelector* it = &component;
-    for (; it && it->relation() == CSSSelector::SubSelector; it = it->tagHistory()) {
+    for (; it && it->relation() == CSSSelector::SubSelector; it = it->tagHistory())
         extractValuesforSelector(it, id, className, customPseudoElementName, tagName);
-    }
-    // FIXME: this null check should not be necessary. See crbug.com/358475
     if (it)
         extractValuesforSelector(it, id, className, customPseudoElementName, tagName);
 
     // Prefer rule sets in order of most likely to apply infrequently.
     if (!id.isEmpty()) {
         addToRuleSet(id, ensurePendingRules()->idRules, ruleData);
         return true;
     }
     if (!className.isEmpty()) {
         addToRuleSet(className, ensurePendingRules()->classRules, ruleData);
@@ skipping 216 matching lines @@
 
 #ifndef NDEBUG
 void RuleSet::show()
 {
     for (const auto& rule: m_allRules)
         rule.selector().show();
 }
 #endif
 
 } // namespace blink