Store :last/first-child state as restyle flags.

Source/core/css/SelectorChecker.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, 2013 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 600 matching lines @@
                 else if (element.renderStyle() && (element.document().styleEngine()->usesSiblingRules() || element.renderStyle()->unique()))
                     element.renderStyle()->setEmptyState(result);
             }
             return result;
         }
     case CSSSelector::PseudoFirstChild:
         // first-child matches the first child that is an element
         if (ContainerNode* parent = element.parentElementOrDocumentFragment()) {
             bool result = siblingTraversalStrategy.isFirstChild(element);
             if (m_mode == ResolvingStyle) {
-                RenderStyle* childStyle = context.elementStyle ? context.elementStyle : element.renderStyle();
                 parent->setChildrenAffectedByFirstChildRules();
-                if (result && childStyle)
-                    childStyle->setFirstChildState();
+                element.setAffectedByFirstChildRules();
             }
             return result;
         }
         break;
     case CSSSelector::PseudoFirstOfType:
         // first-of-type matches the first element of its type
         if (ContainerNode* parent = element.parentElementOrDocumentFragment()) {
             bool result = siblingTraversalStrategy.isFirstOfType(element, element.tagQName());
             if (m_mode == ResolvingStyle)
                 parent->setChildrenAffectedByForwardPositionalRules();
             return result;
         }
         break;
     case CSSSelector::PseudoLastChild:
         // last-child matches the last child that is an element
         if (ContainerNode* parent = element.parentElementOrDocumentFragment()) {
             bool result = parent->isFinishedParsingChildren() && siblingTraversalStrategy.isLastChild(element);
             if (m_mode == ResolvingStyle) {
-                RenderStyle* childStyle = context.elementStyle ? context.elementStyle : element.renderStyle();
                 parent->setChildrenAffectedByLastChildRules();
-                if (result && childStyle)
-                    childStyle->setLastChildState();
+                element.setAffectedByLastChildRules();
             }
             return result;
         }
         break;
     case CSSSelector::PseudoLastOfType:
         // last-of-type matches the last element of its type
         if (ContainerNode* parent = element.parentElementOrDocumentFragment()) {
             if (m_mode == ResolvingStyle)
                 parent->setChildrenAffectedByBackwardPositionalRules();
             if (!parent->isFinishedParsingChildren())
                 return false;
             return siblingTraversalStrategy.isLastOfType(element, element.tagQName());
         }
         break;
     case CSSSelector::PseudoOnlyChild:
         if (ContainerNode* parent = element.parentElementOrDocumentFragment()) {
             bool firstChild = siblingTraversalStrategy.isFirstChild(element);
             bool onlyChild = firstChild && parent->isFinishedParsingChildren() && siblingTraversalStrategy.isLastChild(element);
             if (m_mode == ResolvingStyle) {
-                RenderStyle* childStyle = context.elementStyle ? context.elementStyle : element.renderStyle();
                 parent->setChildrenAffectedByFirstChildRules();
                 parent->setChildrenAffectedByLastChildRules();
-                if (firstChild && childStyle)
-                    childStyle->setFirstChildState();
-                if (onlyChild && childStyle)
-                    childStyle->setLastChildState();
+                element.setAffectedByFirstChildRules();
+                element.setAffectedByLastChildRules();

[esprehn, 2014/11/24 18:46:05]

Why not check firstChild and onlyChild like before?

             }
             return onlyChild;
         }
         break;
     case CSSSelector::PseudoOnlyOfType:
         // FIXME: This selector is very slow.
         if (ContainerNode* parent = element.parentElementOrDocumentFragment()) {
             if (m_mode == ResolvingStyle) {
                 parent->setChildrenAffectedByForwardPositionalRules();
                 parent->setChildrenAffectedByBackwardPositionalRules();
@@ skipping 497 matching lines @@
     return isHTMLSelectElement(element) && !toHTMLSelectElement(element).usesMenuList();
 }
 
 template
 SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext&, const DOMSiblingTraversalStrategy&, MatchResult*) const;
 
 template
 SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext&, const ShadowDOMSiblingTraversalStrategy&, MatchResult*) const;
 
 }