Clean compiling warnings on Linux

xfa/src/fxbarcode/BC_TwoDimWriter.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_SRC_FXBARCODE_BC_TWODIMWRITER_H_
 #define XFA_SRC_FXBARCODE_BC_TWODIMWRITER_H_
 
 #include "xfa/src/fxbarcode/BC_Writer.h"
 
 class CBC_CommonBitMatrix;
 
 class CBC_TwoDimWriter : public CBC_Writer {
  public:
   CBC_TwoDimWriter();
   virtual ~CBC_TwoDimWriter();
-  virtual uint8_t* Encode(const CFX_WideString& contents,
-                          int32_t ecLevel,
-                          int32_t& outWidth,
-                          int32_t& outHeight,
-                          int32_t& e) {
-    return nullptr;
-  };
-  virtual uint8_t* Encode(const CFX_ByteString& contents,
-                          BCFORMAT format,
-                          int32_t& outWidth,
-                          int32_t& outHeight,
-                          int32_t hints,
-                          int32_t& e) {
-    return nullptr;
-  };
-  virtual uint8_t* Encode(const CFX_ByteString& contents,
-                          BCFORMAT format,
-                          int32_t& outWidth,
-                          int32_t& outHeight,
-                          int32_t& e) {
-    return nullptr;
-  };
   virtual void RenderResult(uint8_t* code,
                             int32_t codeWidth,
                             int32_t codeHeight,
                             int32_t& e);
   virtual void RenderBitmapResult(CFX_DIBitmap*& pOutBitmap, int32_t& e);
   virtual void RenderDeviceResult(CFX_RenderDevice* device,
                                   const CFX_Matrix* matrix);
   virtual FX_BOOL SetErrorCorrectionLevel(int32_t level) = 0;
   virtual int32_t GetErrorCorrectionLevel() { return m_iCorrectLevel; };
 
  protected:
   int32_t m_iCorrectLevel;
   FX_BOOL m_bFixedSize;
   CBC_CommonBitMatrix* m_output;
 };
 
 #endif  // XFA_SRC_FXBARCODE_BC_TWODIMWRITER_H_