Replace style sharing cousin list search with LRU

Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1496 matching lines @@
         if (document()->styleSheetCollection()->usesRemUnits() && document()->documentElement() == this && localChange != NoChange && currentStyle && newStyle && currentStyle->fontSize() != newStyle->fontSize()) {
             // Cached RenderStyles may depend on the re units.
             document()->styleResolver()->invalidateMatchedPropertiesCache();
             change = Force;
         }
 
         if (styleChangeType() >= SubtreeStyleChange)
             change = Force;
         else if (change != Force)
             change = localChange;
+    } else {
+        // We still want to seed the style sharing list when just walking the tree to maximize sharing.
+        document()->styleResolver()->addToStyleSharingList(this);
     }
     StyleResolverParentPusher parentPusher(this);
 
     for (ShadowRoot* root = youngestShadowRoot(); root; root = root->olderShadowRoot()) {
         if (shouldRecalcStyle(change, root)) {
             parentPusher.push();
             root->recalcStyle(change);
         }
     }
 
@@ skipping 24 matching lines @@
 
             if (forceCheckOfNextElementSibling || forceCheckOfAnyElementSibling)
                 element->setNeedsStyleRecalc();
 
             forceCheckOfNextElementSibling = childRulesChanged && hasDirectAdjacentRules;
             forceCheckOfAnyElementSibling = forceCheckOfAnyElementSibling || (childRulesChanged && hasIndirectAdjacentRules);
 
             if (shouldRecalcStyle(change, element)) {
                 parentPusher.push();
                 didReattach = element->recalcStyle(change);
+            } else {
+                document()->styleResolver()->addToStyleSharingList(element);
             }
         }
 
         forceReattachOfAnyWhitespaceSibling = didReattach || forceReattachOfAnyWhitespaceSibling;
     }
 
     if (shouldRecalcStyle(change, this)) {
         updatePseudoElement(AFTER, change);
         updatePseudoElement(BACKDROP, change);
     }
@@ skipping 2072 matching lines @@
     return 0;
 }
 
 Attribute* UniqueElementData::attributeItem(unsigned index)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(index < length());
     return &m_attributeVector.at(index);
 }
 
 } // namespace WebCore