Oilpan: remove unused support for removing FrameDestructionObservers.

Source/core/frame/LocalFrame.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Simon Hausmann <hausmann@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  *                     2001 George Staikos <staikos@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov <ap@nypop.com>
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 290 matching lines @@
 
     for (size_t i = 0; i < childFrames.size(); ++i)
         childFrames[i]->didChangeVisibilityState();
 }
 
 void LocalFrame::addDestructionObserver(FrameDestructionObserver* observer)
 {
     m_destructionObservers.add(observer);
 }
 
+#if !ENABLE(OILPAN)
 void LocalFrame::removeDestructionObserver(FrameDestructionObserver* observer)
 {
     m_destructionObservers.remove(observer);
 }
+#endif
 
 void LocalFrame::willDetachFrameHost()
 {
     // We should never be detatching the page during a Layout.
     RELEASE_ASSERT(!m_view || !m_view->isInPerformLayout());
 
     Frame* parent = tree().parent();
     if (parent && parent->isLocalFrame())
         toLocalFrame(parent)->loader().checkLoadComplete();
 
@@ skipping 406 matching lines @@
 
     return curFrame;
 }
 
 void LocalFrame::setPagePopupOwner(Element& owner)
 {
     m_pagePopupOwner = &owner;
 }
 
 } // namespace blink