Oilpan: have FrameFetchContext keep a DocumentLoader member.

Source/core/loader/FrameFetchContext.h

Index: Source/core/loader/FrameFetchContext.h
diff --git a/Source/core/loader/FrameFetchContext.h b/Source/core/loader/FrameFetchContext.h
index f4b79eb40ec58b5b3fff0b0d987f2429d125402d..cd99cf9d726a4e09c086bbaeb2d20cc024b219af 100644
--- a/Source/core/loader/FrameFetchContext.h
+++ b/Source/core/loader/FrameFetchContext.h
@@ -123,7 +123,7 @@ private:
     // currently leak because ComputedStyle and its data are not on the heap.
     // See crbug.com/383860 for details.
     RawPtrWillBeWeakMember<Document> m_document;
-    DocumentLoader* m_documentLoader;
+    RawPtrWillBeMember<DocumentLoader> m_documentLoader;
 };
 
 }