Oilpan: Ensure that classes with virtual trace methods always have vtables for their left-most base…

Source/platform/network/SocketStreamHandle.h

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2009, 2011, 2012 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 44 matching lines @@
     SocketStreamState state() const;
 
     void connect(const KURL&);
     bool send(const char* data, int length);
     void close(); // Disconnect after all data in buffer are sent.
     void disconnect();
 
     SocketStreamHandleClient* client() const { return m_client; }
     void setClient(SocketStreamHandleClient*);
 
-    void trace(Visitor*);
+    virtual void trace(Visitor*);
 
 private:
     explicit SocketStreamHandle(SocketStreamHandleClient*);
 
     bool sendPendingData();
 
     int sendInternal(const char* data, int length);
     void closeInternal();
 
     Member<SocketStreamHandleClient> m_client;
     StreamBuffer<char, 1024 * 1024> m_buffer;
     SocketStreamState m_state;
 
     friend class SocketStreamHandleInternal;
     Member<SocketStreamHandleInternal> m_internal;
 };
 
 } // namespace blink
 
 #endif // SocketStreamHandle_h