Replace style sharing cousin list search with LRU

Source/core/dom/ContainerNode.cpp

Index: Source/core/dom/ContainerNode.cpp
diff --git a/Source/core/dom/ContainerNode.cpp b/Source/core/dom/ContainerNode.cpp
index 1b26b71ed4092b7f264fd8962e5148ff451b7108..2c57b317afe95a14b8b7757caead819a8a106b98 100644
--- a/Source/core/dom/ContainerNode.cpp
+++ b/Source/core/dom/ContainerNode.cpp
@@ -25,6 +25,7 @@
 
 #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"
@@ -1036,6 +1037,8 @@ static void updateTreeAfterInsertion(ContainerNode* parent, Node* child, AttachB
             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);