Use exactly one of final, override, and virtual

util/file/file_writer.h

Index: util/file/file_writer.h
diff --git a/util/file/file_writer.h b/util/file/file_writer.h
index e454848d78714530b934320e846bb2cfe5e3b1c4..54c59c923378f58f9e8bffe5a8207e9ae764b0c4 100644
--- a/util/file/file_writer.h
+++ b/util/file/file_writer.h
@@ -105,19 +105,19 @@ class FileWriter : public FileWriterInterface {
   //!
   //! \note It is only valid to call this method between a successful Open() and
   //!     a Close().
-  virtual bool Write(const void* data, size_t size) override;
+  bool Write(const void* data, size_t size) override;
 
   //! \copydoc FileWriterInterface::WriteIoVec()
   //!
   //! \note It is only valid to call this method between a successful Open() and
   //!     a Close().
-  virtual bool WriteIoVec(std::vector<WritableIoVec>* iovecs) override;
+  bool WriteIoVec(std::vector<WritableIoVec>* iovecs) override;
 
   //! \copydoc FileWriterInterface::Seek()
   //!
   //! \note It is only valid to call this method between a successful Open() and
   //!     a Close().
-  virtual off_t Seek(off_t offset, int whence) override;
+  off_t Seek(off_t offset, int whence) override;
 
  private:
   base::ScopedFD fd_;