[oilpan]: Remove support for tracing off-heap hashmaps.

Source/core/dom/StyleEngine.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 661 matching lines @@
     if (!document().isActive())
         return;
 
     if (m_resolver)
         m_resolver->invalidateMatchedPropertiesCache();
     document().setNeedsStyleRecalc(SubtreeStyleChange);
 }
 
 void StyleEngine::trace(Visitor* visitor)
 {
+#if ENABLE(OILPAN)
     visitor->trace(m_document);
     visitor->trace(m_injectedAuthorStyleSheets);
     visitor->trace(m_authorStyleSheets);
     visitor->trace(m_documentStyleSheetCollection);
     visitor->trace(m_styleSheetCollectionMap);
     visitor->trace(m_resolver);
     visitor->trace(m_fontSelector);
     visitor->trace(m_textToSheetCache);
     visitor->trace(m_sheetToTextCache);
     visitor->trace(m_xslStyleSheet);
+#endif
     CSSFontSelectorClient::trace(visitor);
 }
 
 }