Revert "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 0fb80f01519cfe8caa782915d4fdafbaa92f9432..1b26b71ed4092b7f264fd8962e5148ff451b7108 100644
--- a/Source/core/dom/ContainerNode.cpp
+++ b/Source/core/dom/ContainerNode.cpp
@@ -25,7 +25,6 @@
 
 #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"
@@ -683,8 +682,6 @@ void ContainerNode::resumePostAttachCallbacks()
 
         if (s_postAttachCallbackQueue)
             dispatchPostAttachCallbacks();
-        if (StyleResolver* resolver = document()->styleResolverIfExists())
-            resolver->clearStyleSharingList();
     }
     --s_attachDepth;
 }
@@ -1039,8 +1036,6 @@ static void updateTreeAfterInsertion(ContainerNode* parent, Node* child, AttachB
             child->lazyAttach();
         else
             child->attach();
-        if (StyleResolver* resolver = parent->document()->document()->styleResolverIfExists())
-            resolver->clearStyleSharingList();
     }
 
     dispatchChildInsertionEvents(child);