Let querySelector(All) match (nth-)last with unclosed parent.

third_party/WebKit/Source/core/css/SelectorChecker.cpp

Index: third_party/WebKit/Source/core/css/SelectorChecker.cpp
diff --git a/third_party/WebKit/Source/core/css/SelectorChecker.cpp b/third_party/WebKit/Source/core/css/SelectorChecker.cpp
index 532dfd82e3911facd01cfd03ee3f0c5717e3415c..cd7b522d97bcf4f40563d7ff99a70615038d84a1 100644
--- a/third_party/WebKit/Source/core/css/SelectorChecker.cpp
+++ b/third_party/WebKit/Source/core/css/SelectorChecker.cpp
@@ -745,7 +745,7 @@ bool SelectorChecker::checkPseudoClass(const SelectorCheckingContext& context,
           parent->setChildrenAffectedByLastChildRules();
           element.setAffectedByLastChildRules();
         }
-        if (!parent->isFinishedParsingChildren())
+        if (!m_isQuerySelector && !parent->isFinishedParsingChildren())
           return false;
         return isLastChild(element);
       }
@@ -754,7 +754,7 @@ bool SelectorChecker::checkPseudoClass(const SelectorCheckingContext& context,
       if (ContainerNode* parent = element.parentElementOrDocumentFragment()) {
         if (m_mode == ResolvingStyle)
           parent->setChildrenAffectedByBackwardPositionalRules();
-        if (!parent->isFinishedParsingChildren())
+        if (!m_isQuerySelector && !parent->isFinishedParsingChildren())
           return false;
         return isLastOfType(element, element.tagQName());
       }
@@ -767,7 +767,7 @@ bool SelectorChecker::checkPseudoClass(const SelectorCheckingContext& context,
           element.setAffectedByFirstChildRules();
           element.setAffectedByLastChildRules();
         }
-        if (!parent->isFinishedParsingChildren())
+        if (!m_isQuerySelector && !parent->isFinishedParsingChildren())
           return false;
         return isFirstChild(element) && isLastChild(element);
       }
@@ -779,7 +779,7 @@ bool SelectorChecker::checkPseudoClass(const SelectorCheckingContext& context,
           parent->setChildrenAffectedByForwardPositionalRules();
           parent->setChildrenAffectedByBackwardPositionalRules();
         }
-        if (!parent->isFinishedParsingChildren())
+        if (!m_isQuerySelector && !parent->isFinishedParsingChildren())
           return false;
         return isFirstOfType(element, element.tagQName()) &&
                isLastOfType(element, element.tagQName());
@@ -807,7 +807,7 @@ bool SelectorChecker::checkPseudoClass(const SelectorCheckingContext& context,
       if (ContainerNode* parent = element.parentElementOrDocumentFragment()) {
         if (m_mode == ResolvingStyle)
           parent->setChildrenAffectedByBackwardPositionalRules();
-        if (!parent->isFinishedParsingChildren())
+        if (!m_isQuerySelector && !parent->isFinishedParsingChildren())
           return false;
         return selector.matchNth(NthIndexCache::nthLastChildIndex(element));
       }
@@ -816,7 +816,7 @@ bool SelectorChecker::checkPseudoClass(const SelectorCheckingContext& context,
       if (ContainerNode* parent = element.parentElementOrDocumentFragment()) {
         if (m_mode == ResolvingStyle)
           parent->setChildrenAffectedByBackwardPositionalRules();
-        if (!parent->isFinishedParsingChildren())
+        if (!m_isQuerySelector && !parent->isFinishedParsingChildren())
           return false;
         return selector.matchNth(NthIndexCache::nthLastOfTypeIndex(element));
       }