Oilpan: move HistoryItem to the heap.

Source/core/loader/FrameLoader.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) Research In Motion Limited 2009. All rights reserved.
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
@@ skipping 221 matching lines @@
 
     // Document loaders for the three phases of frame loading. Note that while
     // a new request is being loaded, the old document loader may still be referenced.
     // E.g. while a new request is in the "policy" state, the old document loader may
     // be consulted in particular as it makes sense to imply certain settings on the new loader.
     RefPtr<DocumentLoader> m_documentLoader;
     RefPtr<DocumentLoader> m_provisionalDocumentLoader;
     RefPtr<DocumentLoader> m_policyDocumentLoader;
     OwnPtrWillBeMember<FetchContext> m_fetchContext;
 
-    RefPtr<HistoryItem> m_currentItem;
-    RefPtr<HistoryItem> m_provisionalItem;
+    RefPtrWillBeMember<HistoryItem> m_currentItem;
+    RefPtrWillBeMember<HistoryItem> m_provisionalItem;
+
     struct DeferredHistoryLoad {
+        DISALLOW_ALLOCATION();
+    public:
         DeferredHistoryLoad(HistoryItem* item, HistoryLoadType type, ResourceRequestCachePolicy cachePolicy)
             : m_item(item)
             , m_type(type)
             , m_cachePolicy(cachePolicy)
         {
         }
 
         DeferredHistoryLoad() { }
 
         bool isValid() { return m_item; }
 
-        RefPtr<HistoryItem> m_item;
+        void trace(Visitor* visitor)
+        {
+            visitor->trace(m_item);
+        }
+
+        RefPtrWillBeMember<HistoryItem> m_item;
         HistoryLoadType m_type;
         ResourceRequestCachePolicy m_cachePolicy;
     };
+
     DeferredHistoryLoad m_deferredHistoryLoad;
 
     bool m_inStopAllLoaders;
 
     Timer<FrameLoader> m_checkTimer;
 
     bool m_didAccessInitialDocument;
     Timer<FrameLoader> m_didAccessInitialDocumentTimer;
 
     SandboxFlags m_forcedSandboxFlags;
 };
 
 } // namespace blink
 
 #endif // FrameLoader_h