Oilpan: Replace RefPtrs to Node and its subclasses in core/dom/ with Oilpan transtion types.

Source/core/dom/IncrementLoadEventDelayCount.h

Index: Source/core/dom/IncrementLoadEventDelayCount.h
diff --git a/Source/core/dom/IncrementLoadEventDelayCount.h b/Source/core/dom/IncrementLoadEventDelayCount.h
index d588de22a6181a920dbe918b2c8f59de97c1ef8c..b90b5201ee2f595b8bbc1151deb61360bb778e3d 100644
--- a/Source/core/dom/IncrementLoadEventDelayCount.h
+++ b/Source/core/dom/IncrementLoadEventDelayCount.h
@@ -5,6 +5,7 @@
 #ifndef IncrementLoadEventDelayCount_h
 #define IncrementLoadEventDelayCount_h
 
+#include "platform/heap/Handle.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/RefPtr.h"
 
@@ -25,7 +26,7 @@ public:
     void documentChanged(Document& newDocument);
 
 private:
-    RefPtr<Document> m_document;
+    RefPtrWillBePersistent<Document> m_document;
 };
 }