Make code compile with clang_use_chrome_plugin (part III)

xfa/fxbarcode/datamatrix/BC_DataMatrixReader.h

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef XFA_FXBARCODE_DATAMATRIX_BC_DATAMATRIXREADER_H_
 #define XFA_FXBARCODE_DATAMATRIX_BC_DATAMATRIXREADER_H_
 
 #include "xfa/fxbarcode/BC_Reader.h"
 
 class CBC_BinaryBitmap;
 class CBC_DataMatrixDecoder;
 
 class CBC_DataMatrixReader : public CBC_Reader {
  public:
   CBC_DataMatrixReader();
-  virtual ~CBC_DataMatrixReader();
-  CFX_ByteString Decode(CBC_BinaryBitmap* image, int32_t& e);
-  CFX_ByteString Decode(CBC_BinaryBitmap* image, int hints, int32_t& e);
+  ~CBC_DataMatrixReader() override;
+
+  // CBC_Reader
+  CFX_ByteString Decode(CBC_BinaryBitmap* image, int32_t& e) override;
+  CFX_ByteString Decode(CBC_BinaryBitmap* image,
+                        int hints,
+                        int32_t& e) override;
 
   virtual void Init();
 
  private:
   CBC_DataMatrixDecoder* m_decoder;
 };
 
 #endif  // XFA_FXBARCODE_DATAMATRIX_BC_DATAMATRIXREADER_H_