Replace style sharing cousin list search with LRU

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 1749 matching lines @@
         unscheduleStyleRecalc();
 
         // FIXME: SVG <use> element can schedule a recalc in the middle of an already running one.
         // See StyleSheetCollections::updateActiveStyleSheets.
         if (m_styleSheetCollections->needsUpdateActiveStylesheetsOnStyleRecalc())
             setNeedsStyleRecalc();
 
         m_inStyleRecalc = false;
 
         // Pseudo element removal and similar may only work with these flags still set. Reset them after the style recalc.
-        if (m_styleResolver)
+        if (m_styleResolver) {
             m_styleSheetCollections->resetCSSFeatureFlags(m_styleResolver->ruleFeatureSet());
+            m_styleResolver->clearStyleSharingList();
+        }
 
         if (frameView) {
             frameView->resumeScheduledEvents();
             frameView->endDeferredRepaints();
         }
     }
 
     STYLE_STATS_PRINT();
     STYLE_STATS_CLEAR();
 
@@ skipping 265 matching lines @@
     setRenderer(0);
 
     m_hoverNode = 0;
     m_focusedElement = 0;
     m_activeElement = 0;
 
     ContainerNode::detach(context);
 
     unscheduleStyleRecalc();
 
+    clearStyleResolver();
+
     if (render)
         render->destroy();
 
     if (m_touchEventTargets && m_touchEventTargets->size() && parentDocument())
         parentDocument()->didRemoveEventTargetNode(this);
 
     // This is required, as our Frame might delete itself as soon as it detaches
     // us. However, this violates Node::detach() semantics, as it's never
     // possible to re-attach. Eventually Document::detach() should be renamed,
     // or this setting of the frame to 0 could be made explicit in each of the
@@ skipping 3378 matching lines @@
 {
     return DocumentLifecycleNotifier::create(this);
 }
 
 DocumentLifecycleNotifier* Document::lifecycleNotifier()
 {
     return static_cast<DocumentLifecycleNotifier*>(ScriptExecutionContext::lifecycleNotifier());
 }
 
 } // namespace WebCore