Need to check for positional rules on parent with style change.

Source/core/dom/ContainerNode.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2013 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.
@@ skipping 1327 matching lines @@
 
         forceCheckOfAnyElementSibling = forceCheckOfAnyElementSibling || (childRulesChanged && hasIndirectAdjacentRules);
     }
 }
 
 void ContainerNode::checkForSiblingStyleChanges(SiblingCheckType changeType, Node* nodeBeforeChange, Node* nodeAfterChange)
 {
     if (!inActiveDocument() || document().hasPendingForcedStyleRecalc() || styleChangeType() >= SubtreeStyleChange)
         return;
 
-    if (needsStyleRecalc() && childrenAffectedByPositionalRules())
-        return;
-
     // Forward positional selectors include nth-child, nth-of-type, first-of-type and only-of-type.
     // The indirect adjacent selector is the ~ selector.
     // Backward positional selectors include nth-last-child, nth-last-of-type, last-of-type and only-of-type.
     // We have to invalidate everything following the insertion point in the forward and indirect adjacent case,
     // and everything before the insertion point in the backward case.
     // |afterChange| is 0 in the parser callback case, so we won't do any work for the forward case if we don't have to.
     // For performance reasons we just mark the parent node as changed, since we don't want to make childrenChanged O(n^2) by crawling all our kids
     // here. recalcStyle will then force a walk of the children when it sees that this has happened.
     if (((childrenAffectedByForwardPositionalRules() || childrenAffectedByIndirectAdjacentRules()) && nodeAfterChange)
         || (childrenAffectedByBackwardPositionalRules() && nodeBeforeChange)) {
@@ skipping 153 matching lines @@
         return true;
 
     if (node->isElementNode() && toElement(node)->shadow())
         return true;
 
     return false;
 }
 #endif
 
 } // namespace blink