Oilpan: Replace RefPtrs to Node and its subclasses in core/loader with Oilpan transition types.

Source/core/loader/NavigationScheduler.cpp

Index: Source/core/loader/NavigationScheduler.cpp
diff --git a/Source/core/loader/NavigationScheduler.cpp b/Source/core/loader/NavigationScheduler.cpp
index 6b82cac3a77534c30efce12d10eee753e49f177c..2a396ff368ae4591ff8184ace2ef28984cc0b807 100644
--- a/Source/core/loader/NavigationScheduler.cpp
+++ b/Source/core/loader/NavigationScheduler.cpp
@@ -118,7 +118,7 @@ protected:
     const Referrer& referrer() const { return m_referrer; }
 
 private:
-    RefPtr<Document> m_originDocument;
+    RefPtrWillBePersistent<Document> m_originDocument;
     String m_url;
     Referrer m_referrer;
 };