Oilpan: Remove support for tracing of off-heap ListHashSets.

Source/core/css/CSSSegmentedFontFace.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 194 matching lines @@
 void CSSSegmentedFontFace::match(const String& text, WillBeHeapVector<RefPtrWillBeMember<FontFace> >& faces) const
 {
     for (FontFaceList::const_iterator it = m_fontFaces.begin(); it != m_fontFaces.end(); ++it) {
         if ((*it)->cssFontFace()->ranges().intersectsWith(text))
             faces.append(*it);
     }
 }
 
 void CSSSegmentedFontFace::trace(Visitor* visitor)
 {
+#if ENABLE(OILPAN)
     visitor->trace(m_fontSelector);
     visitor->trace(m_fontFaces);
+#endif
 }
 
 }