Oilpan: Prepare to move RenderObject and RenderObjectChildList to Oilpan heap.

Source/core/rendering/RenderTextFragment.h

Index: Source/core/rendering/RenderTextFragment.h
diff --git a/Source/core/rendering/RenderTextFragment.h b/Source/core/rendering/RenderTextFragment.h
index 45a385bc0bc715515b005a852256ecef3d96b72d..e81c88de0e4946cf4b066a1a878ddb4c623fde0c 100644
--- a/Source/core/rendering/RenderTextFragment.h
+++ b/Source/core/rendering/RenderTextFragment.h
@@ -36,6 +36,7 @@ public:
     RenderTextFragment(Node*, StringImpl*, int startOffset, int length);
     RenderTextFragment(Node*, StringImpl*);
     virtual ~RenderTextFragment();
+    virtual void trace(Visitor*) OVERRIDE;
 
     virtual bool isTextFragment() const OVERRIDE { return true; }
 
@@ -69,7 +70,7 @@ private:
     unsigned m_start;
     unsigned m_end;
     RefPtr<StringImpl> m_contentString;
-    RenderBoxModelObject* m_firstLetter;
+    RawPtrWillBeMember<RenderBoxModelObject> m_firstLetter;
 };
 
 DEFINE_TYPE_CASTS(RenderTextFragment, RenderObject, object, toRenderText(object)->isTextFragment(), toRenderText(object).isTextFragment());