Oilpan: Make the Node hierarchy RefCountedGarbageCollected instead of TreeShared.

Source/core/dom/TreeScope.h

Index: Source/core/dom/TreeScope.h
diff --git a/Source/core/dom/TreeScope.h b/Source/core/dom/TreeScope.h
index 9c61b1bebbd832f48714fab105bba36c7d6459de..6862f82423a99157c3324d448c717684d55adea2 100644
--- a/Source/core/dom/TreeScope.h
+++ b/Source/core/dom/TreeScope.h
@@ -157,8 +157,11 @@ protected:
 private:
     virtual void dispose() { }
 
+#if !ENABLE(OILPAN)
     int refCount() const;
-#if SECURITY_ASSERT_ENABLED
+#endif
+
+#if SECURITY_ASSERT_ENABLED && !ENABLE(OILPAN)
     bool deletionHasBegun();
     void beginDeletion();
 #else
@@ -169,7 +172,7 @@ private:
     bool rootNodeHasTreeSharedParent() const;
 
     Node& m_rootNode;
-    Document* m_document;
+    RawPtrWillBeMember<Document> m_document;
     RawPtrWillBeMember<TreeScope> m_parentTreeScope;
 
 #if !ENABLE(OILPAN)