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

Source/core/dom/Node.h

Index: Source/core/dom/Node.h
diff --git a/Source/core/dom/Node.h b/Source/core/dom/Node.h
index 83c2579377172bbfe2b32eb5e2b25408125261a3..173f301ab79e81a089d5b32015c6693cad51338f 100644
--- a/Source/core/dom/Node.h
+++ b/Source/core/dom/Node.h
@@ -105,7 +105,10 @@ protected:
         : m_renderer(renderer)
     { }
 
-private:
+protected:
+    // Oilpan: This member is traced in NodeRareData.
+    // FIXME: Can we add traceAfterDispatch and finalizeGarbageCollectedObject
+    // to NodeRareDataBase, and make m_renderer Member<>?
     RenderObject* m_renderer;
 };