Oilpan: remove unused support for removing FrameDestructionObservers.

Source/core/frame/LocalFrame.h

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999-2001 Lars Knoll <knoll@kde.org>
  *                     1999-2001 Antti Koivisto <koivisto@kde.org>
  *                     2000-2001 Simon Hausmann <hausmann@kde.org>
  *                     2000-2001 Dirk Mueller <mueller@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
@@ skipping 63 matching lines @@
         void createView(const IntSize&, const Color&, bool,
             ScrollbarMode = ScrollbarAuto, bool horizontalLock = false,
             ScrollbarMode = ScrollbarAuto, bool verticalLock = false);
 
         virtual ~LocalFrame();
         virtual void trace(Visitor*) OVERRIDE;
 
         virtual void detach() OVERRIDE;
 
         void addDestructionObserver(FrameDestructionObserver*);
+#if !ENABLE(OILPAN)
         void removeDestructionObserver(FrameDestructionObserver*);
+#endif
 
         void willDetachFrameHost();
         void detachFromFrameHost();
 
         virtual void disconnectOwnerElement() OVERRIDE;
 
         virtual void setDOMWindow(PassRefPtrWillBeRawPtr<LocalDOMWindow>) OVERRIDE;
         FrameView* view() const;
         Document* document() const;
         void setPagePopupOwner(Element&);
@@ skipping 160 matching lines @@
     DEFINE_TYPE_CASTS(LocalFrame, Frame, localFrame, localFrame->isLocalFrame(), localFrame.isLocalFrame());
 
 } // namespace blink
 
 // During refactoring, there are some places where we need to do type conversions that
 // will not be needed once all instances of LocalFrame and RemoteFrame are sorted out.
 // At that time this #define will be removed and all the uses of it will need to be corrected.
 #define toLocalFrameTemporary toLocalFrame
 
 #endif // LocalFrame_h