Oilpan: Support nested pre-finalizers

Source/core/frame/LocalDOMWindow.h

Index: Source/core/frame/LocalDOMWindow.h
diff --git a/Source/core/frame/LocalDOMWindow.h b/Source/core/frame/LocalDOMWindow.h
index 0e23dc224aec33ae01d86562c00ce868f9065ee2..141d68f4af9354197be2808f26064784724334c4 100644
--- a/Source/core/frame/LocalDOMWindow.h
+++ b/Source/core/frame/LocalDOMWindow.h
@@ -75,7 +75,6 @@ public:
     }
 
     virtual ~LocalDOMWindow();
-    void dispose();
 
     DECLARE_VIRTUAL_TRACE();
 
@@ -235,6 +234,7 @@ private:
     friend WTF::OwnedPtrDeleter<WindowFrameObserver>;
 
     explicit LocalDOMWindow(LocalFrame&);
+    void dispose();
 
     Page* page();