Update {virtual,override} to follow C++11 style in components.

components/nacl/broker/nacl_broker_listener.h

Index: components/nacl/broker/nacl_broker_listener.h
diff --git a/components/nacl/broker/nacl_broker_listener.h b/components/nacl/broker/nacl_broker_listener.h
index 46dc9023e2feb8fd1aaf980c3419f68b8810ef65..61d2651ed31facc9218a19d07f7759d347fb4d81 100644
--- a/components/nacl/broker/nacl_broker_listener.h
+++ b/components/nacl/broker/nacl_broker_listener.h
@@ -21,18 +21,17 @@ class NaClBrokerListener : public content::SandboxedProcessLauncherDelegate,
                            public IPC::Listener {
  public:
   NaClBrokerListener();
-  ~NaClBrokerListener();
+  ~NaClBrokerListener() override;
 
   void Listen();
 
   // content::SandboxedProcessLauncherDelegate implementation:
-  virtual void PreSpawnTarget(sandbox::TargetPolicy* policy,
-                              bool* success) override;
+  void PreSpawnTarget(sandbox::TargetPolicy* policy, bool* success) override;
 
   // IPC::Listener implementation.
-  virtual void OnChannelConnected(int32 peer_pid) override;
-  virtual bool OnMessageReceived(const IPC::Message& msg) override;
-  virtual void OnChannelError() override;
+  void OnChannelConnected(int32 peer_pid) override;
+  bool OnMessageReceived(const IPC::Message& msg) override;
+  void OnChannelError() override;
 
  private:
   void OnLaunchLoaderThroughBroker(const std::string& loader_channel_id);