Oilpan: Remove support for tracing off-heap HashSets.

Source/core/svg/SVGCursorElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 106 matching lines @@
     // Any change of a cursor specific attribute triggers this recalc.
     WillBeHeapHashSet<RawPtrWillBeWeakMember<SVGElement> >::const_iterator it = m_clients.begin();
     WillBeHeapHashSet<RawPtrWillBeWeakMember<SVGElement> >::const_iterator end = m_clients.end();
 
     for (; it != end; ++it)
         (*it)->setNeedsStyleRecalc(SubtreeStyleChange);
 }
 
 void SVGCursorElement::trace(Visitor* visitor)
 {
+#if ENABLE(OILPAN)
     visitor->trace(m_clients);
+#endif
     SVGElement::trace(visitor);
 }
 
 }