Oilpan: Change Persistent members of Resource subclasses to Member.

Source/core/fetch/DocumentResource.h

Index: Source/core/fetch/DocumentResource.h
diff --git a/Source/core/fetch/DocumentResource.h b/Source/core/fetch/DocumentResource.h
index e32fd1dc5b9735aef897831f2be48da2adc4e5d4..6f9b8cda9028bf1aed641dfe09f86c30fb773e72 100644
--- a/Source/core/fetch/DocumentResource.h
+++ b/Source/core/fetch/DocumentResource.h
@@ -38,6 +38,7 @@ public:
 
     DocumentResource(const ResourceRequest&, Type);
     virtual ~DocumentResource();
+    virtual void trace(Visitor*) OVERRIDE;
 
     Document* document() const { return m_document.get(); }
 
@@ -48,7 +49,7 @@ public:
 private:
     PassRefPtrWillBeRawPtr<Document> createDocument(const KURL&);
 
-    RefPtrWillBePersistent<Document> m_document;
+    RefPtrWillBeMember<Document> m_document;
     OwnPtr<TextResourceDecoder> m_decoder;
 };