Oilpan: Prepare moving AXObject to heap

Source/modules/accessibility/AXMenuListOption.cpp

 /*
  * Copyright (C) 2010 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 97 matching lines @@
     ASSERT(grandparent->isMenuList());
 
     return grandparent->elementRect();
 }
 
 String AXMenuListOption::stringValue() const
 {
     return m_element->text();
 }
 
+DEFINE_TRACE(AXMenuListOption)
+{
+    AXMockObject::trace(visitor);
+    visitor->trace(m_element);
+}
+
 } // namespace blink