Standardize usage of virtual/override/final in remoting/

remoting/host/posix/signal_handler.cc

Index: remoting/host/posix/signal_handler.cc
diff --git a/remoting/host/posix/signal_handler.cc b/remoting/host/posix/signal_handler.cc
index db9d0ee6df7061b200f889ea26393f49eb3c49c2..30abf59d15d179d358453ed4b9bf4f6f2bb7c673 100644
--- a/remoting/host/posix/signal_handler.cc
+++ b/remoting/host/posix/signal_handler.cc
@@ -27,8 +27,8 @@ class SignalListener : public base::MessagePumpLibevent::Watcher {
 
   void AddSignalHandler(int signal, const SignalHandler& handler);
 
-  virtual void OnFileCanReadWithoutBlocking(int fd) override;
-  virtual void OnFileCanWriteWithoutBlocking(int fd) override {}
+  void OnFileCanReadWithoutBlocking(int fd) override;
+  void OnFileCanWriteWithoutBlocking(int fd) override {}
 
   // WatchFileDescriptor needs a controller through which the operation can be
   // canceled. We don't use it, but this is as good a place as any to store it.