Oilpan: fix build++ after r192490.

Source/core/dom/DOMSettableTokenList.cpp

 /*
  * Copyright (C) 2010 Google 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 22 matching lines @@
     : m_value()
     , m_tokens()
     , m_observer(observer)
 {
 }
 
 DOMSettableTokenList::~DOMSettableTokenList()
 {
 }
 
+DEFINE_TRACE(DOMSettableTokenList)
+{
+    visitor->trace(m_observer);
+    DOMTokenList::trace(visitor);
+}
+
 const AtomicString DOMSettableTokenList::item(unsigned index) const
 {
     if (index >= length())
         return AtomicString();
     return m_tokens[index];
 }
 
 bool DOMSettableTokenList::containsInternal(const AtomicString& token) const
 {
     return m_tokens.contains(token);
@@ skipping 35 matching lines @@
 
 void DOMSettableTokenList::setValue(const AtomicString& value)
 {
     m_value = value;
     m_tokens.set(value, false);
     if (m_observer)
         m_observer->valueChanged();
 }
 
 } // namespace blink