Standardize usage of virtual/override/final in ipc/

ipc/ipc_test_channel_listener.h

Index: ipc/ipc_test_channel_listener.h
diff --git a/ipc/ipc_test_channel_listener.h b/ipc/ipc_test_channel_listener.h
index 228cbf717c1a9ff69e4f7343a54a71ac20db671a..ae5288d93d1f106f0b567e344f0845da1d991a13 100644
--- a/ipc/ipc_test_channel_listener.h
+++ b/ipc/ipc_test_channel_listener.h
@@ -20,10 +20,10 @@ class TestChannelListener : public Listener {
   static void SendOneMessage(Sender* sender, const char* text);
 
   TestChannelListener() : sender_(NULL), messages_left_(50) {}
-  virtual ~TestChannelListener() {}
+  ~TestChannelListener() override {}
 
-  virtual bool OnMessageReceived(const Message& message) override;
-  virtual void OnChannelError() override;
+  bool OnMessageReceived(const Message& message) override;
+  void OnChannelError() override;
 
   void Init(Sender* s) {
     sender_ = s;