Replace style sharing cousin list search with LRU

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 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * 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.
  */
 
 #include "config.h"
 #include "core/dom/ContainerNode.h"
 
 #include "bindings/v8/ExceptionState.h"
 #include "bindings/v8/ExceptionStatePlaceholder.h"
+#include "core/css/resolver/StyleResolver.h"
 #include "core/dom/ChildListMutationScope.h"
 #include "core/dom/ContainerNodeAlgorithms.h"
 #include "core/dom/EventNames.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/FullscreenElementStack.h"
 #include "core/dom/MutationEvent.h"
 #include "core/dom/NodeRareData.h"
 #include "core/dom/NodeRenderStyle.h"
 #include "core/dom/NodeTraversal.h"
 #include "core/html/HTMLCollection.h"
@@ skipping 991 matching lines @@
 
     ChildNodeInsertionNotifier(parent).notify(child);
 
     // FIXME: Attachment should be the first operation in this function, but some code
     // (for example, HTMLFormControlElement's autofocus support) requires this ordering.
     if (parent->attached() && !child->attached() && child->parentNode() == parent) {
         if (attachBehavior == AttachLazily)
             child->lazyAttach();
         else
             child->attach();
+        if (StyleResolver* resolver = child->document()->styleResolverIfExists())
+            resolver->clearStyleSharingList();

[esprehn, 2013/08/22 17:33:02]

Why do you need to clear the sharing list after inserting a new child? Note that
not all code paths even go through here, so if you need this clearing it here is
incomplete.

     }
 
     dispatchChildInsertionEvents(child);
 }
 
 #ifndef NDEBUG
 bool childAttachedAllowedWhenAttachingChildren(ContainerNode* node)
 {
     if (node->isShadowRoot())
         return true;
 
     if (node->isInsertionPoint())
         return true;
 
     if (node->isElementNode() && toElement(node)->shadow())
         return true;
 
     return false;
 }
 #endif
 
 } // namespace WebCore