Revert of Standardize usage of virtual/override/final in ipc/

ipc/ipc_sync_message_filter.h

Index: ipc/ipc_sync_message_filter.h
diff --git a/ipc/ipc_sync_message_filter.h b/ipc/ipc_sync_message_filter.h
index 49c3ca031719ce0708c48f63d10327fcd3f4b3dd..015cbf8b19dc7c4ec5e9a62931aa1a42fb992289 100644
--- a/ipc/ipc_sync_message_filter.h
+++ b/ipc/ipc_sync_message_filter.h
@@ -31,16 +31,16 @@
   explicit SyncMessageFilter(base::WaitableEvent* shutdown_event);
 
   // MessageSender implementation.
-  bool Send(Message* message) override;
+  virtual bool Send(Message* message) override;
 
   // MessageFilter implementation.
-  void OnFilterAdded(Sender* sender) override;
-  void OnChannelError() override;
-  void OnChannelClosing() override;
-  bool OnMessageReceived(const Message& message) override;
+  virtual void OnFilterAdded(Sender* sender) override;
+  virtual void OnChannelError() override;
+  virtual void OnChannelClosing() override;
+  virtual bool OnMessageReceived(const Message& message) override;
 
  protected:
-  ~SyncMessageFilter() override;
+  virtual ~SyncMessageFilter();
 
  private:
   void SendOnIOThread(Message* message);