Cache element indices for :nth-child and :nth-last-child selectors.

Source/core/css/SiblingTraversalStrategies.h

 /*
  * 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 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 11 matching lines @@
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #ifndef SiblingTraversalStrategies_h
 #define SiblingTraversalStrategies_h
 
+#include "core/dom/Document.h"
 #include "core/dom/Element.h"
 #include "core/dom/ElementTraversal.h"
+#include "core/dom/NthIndexCache.h"
 #include "core/style/ComputedStyle.h"
 
 namespace blink {
 
 class DOMSiblingTraversalStrategy {
 public:
     bool isFirstChild(Element&) const;
     bool isLastChild(Element&) const;
     bool isFirstOfType(Element&, const QualifiedName&) const;
     bool isLastOfType(Element&, const QualifiedName&) const;
@@ skipping 28 matching lines @@
     return !ElementTraversal::previousSibling(element, HasTagName(type));
 }
 
 inline bool DOMSiblingTraversalStrategy::isLastOfType(Element& element, const QualifiedName& type) const
 {
     return !ElementTraversal::nextSibling(element, HasTagName(type));
 }
 
 inline int DOMSiblingTraversalStrategy::countElementsBefore(Element& element) const
 {
+    if (NthIndexCache* nthIndexCache = element.document().nthIndexCache())
+        return nthIndexCache->nthChildIndex(element) - 1;
+
     int count = 0;
     for (const Element* sibling = ElementTraversal::previousSibling(element); sibling; sibling = ElementTraversal::previousSibling(*sibling))
         count++;
 
     return count;
 }
 
 inline int DOMSiblingTraversalStrategy::countElementsOfTypeBefore(Element& element, const QualifiedName& type) const
 {
     int count = 0;
     for (const Element* sibling = ElementTraversal::previousSibling(element, HasTagName(type)); sibling; sibling = ElementTraversal::previousSibling(*sibling, HasTagName(type)))
         ++count;
     return count;
 }
 
 inline int DOMSiblingTraversalStrategy::countElementsAfter(Element& element) const
 {
+    if (NthIndexCache* nthIndexCache = element.document().nthIndexCache())
+        return nthIndexCache->nthLastChildIndex(element) - 1;
+
     int count = 0;
     for (const Element* sibling = ElementTraversal::nextSibling(element); sibling; sibling = ElementTraversal::nextSibling(*sibling))
         ++count;
     return count;
 }
 
 inline int DOMSiblingTraversalStrategy::countElementsOfTypeAfter(Element& element, const QualifiedName& type) const
 {
     int count = 0;
     for (const Element* sibling = ElementTraversal::nextSibling(element, HasTagName(type)); sibling; sibling = ElementTraversal::nextSibling(*sibling, HasTagName(type)))
@@ skipping 121 matching lines @@
         if (m_siblings[i]->isElementNode() && toElement(m_siblings[i])->hasTagName(type))
             return ++count;
     }
 
     return count;
 }
 
 }
 
 #endif