[oilpan] The Node hierarchy should have correct accept method chains

Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. 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.
@@ skipping 575 matching lines @@
     MemoryClassInfo info(memoryObjectInfo, this, WebCoreMemoryTypes::DOM);
     HTMLElement::reportMemoryUsage(memoryObjectInfo);
     info.addMember(m_observers, "observers");
     info.addMember(m_context, "context");
     info.addMember(m_imageBuffer, "imageBuffer");
     info.addMember(m_contextStateSaver, "contextStateSaver");
     info.addMember(m_presentedImage, "presentedImage");
     info.addMember(m_copiedImage, "copiedImage");
 }
 
+void HTMLCanvasElement::acceptHeapVisitor(Visitor* visitor) const
+{
+    HTMLElement::acceptHeapVisitor(visitor);
 }
+
+}