Re-enable several MSVC warnings

core/fxcodec/codec/codec_int.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 CORE_FXCODEC_CODEC_CODEC_INT_H_
 #define CORE_FXCODEC_CODEC_CODEC_INT_H_
 
 #include <limits.h>
@@ skipping 29 matching lines @@
                                                  int nComps,
                                                  int bpc) override;
 };
 
 class CCodec_ScanlineDecoder : public ICodec_ScanlineDecoder {
  public:
   CCodec_ScanlineDecoder();
   ~CCodec_ScanlineDecoder() override;
 
   // ICodec_ScanlineDecoder
-  FX_DWORD GetSrcOffset() override { return -1; }
   void DownScale(int dest_width, int dest_height) override;
   const uint8_t* GetScanline(int line) override;
   FX_BOOL SkipToScanline(int line, IFX_Pause* pPause) override;
   int GetWidth() override { return m_OutputWidth; }
   int GetHeight() override { return m_OutputHeight; }
   int CountComps() override { return m_nComps; }
   int GetBPC() override { return m_bpc; }
   FX_BOOL IsColorTransformed() override { return m_bColorTransformed; }
   void ClearImageData() override { m_pDataCache.reset(); }
 
@@ skipping 358 matching lines @@
 OPJ_SIZE_T opj_read_from_memory(void* p_buffer,
                                 OPJ_SIZE_T nb_bytes,
                                 void* p_user_data);
 OPJ_SIZE_T opj_write_from_memory(void* p_buffer,
                                  OPJ_SIZE_T nb_bytes,
                                  void* p_user_data);
 OPJ_OFF_T opj_skip_from_memory(OPJ_OFF_T nb_bytes, void* p_user_data);
 OPJ_BOOL opj_seek_from_memory(OPJ_OFF_T nb_bytes, void* p_user_data);
 
 #endif  // CORE_FXCODEC_CODEC_CODEC_INT_H_