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

Source/core/html/MediaDocument.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 203 matching lines @@
 
         DocumentLoader* documentLoader = loader();
         ASSERT(documentLoader);
         if (documentLoader)
             embedElement->setAttribute(typeAttr, documentLoader->writer()->mimeType());
 
         videoElement->parentNode()->replaceChild(embedElement.raw(), videoElement, IGNORE_EXCEPTION);
     }
 }
 
+void MediaDocument::acceptHeapVisitor(Visitor* visitor) const
+{
+    HTMLDocument::acceptHeapVisitor(visitor);
 }
+
+}