Cleanup forward declarations.

core/include/fxcodec/fx_codec.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_INCLUDE_FXCODEC_FX_CODEC_H_
 #define CORE_INCLUDE_FXCODEC_FX_CODEC_H_
 
 #include <map>
 #include <memory>
 #include <vector>
 
 #include "core/include/fxcodec/fx_codec_def.h"
 #include "core/include/fxcrt/fx_basic.h"
 #include "core/include/fxcrt/fx_coordinates.h"  // For FX_RECT.
 
 class CFX_DIBSource;
 class CJPX_Decoder;
 class CPDF_ColorSpace;
-class CPDF_PrivateData;
 class CPDF_StreamAcc;
 class ICodec_BasicModule;
 class ICodec_FaxModule;
 class ICodec_FlateModule;
 class ICodec_IccModule;
 class ICodec_Jbig2Encoder;
 class ICodec_Jbig2Module;
 class ICodec_JpegModule;
 class ICodec_JpxModule;
 class ICodec_ScanlineDecoder;
@@ skipping 517 matching lines @@
 FX_BOOL MD5ComputeID(const void* buf, FX_DWORD dwSize, uint8_t ID[16]);
 void FaxG4Decode(const uint8_t* src_buf,
                  FX_DWORD src_size,
                  int* pbitpos,
                  uint8_t* dest_buf,
                  int width,
                  int height,
                  int pitch);
 
 #endif  // CORE_INCLUDE_FXCODEC_FX_CODEC_H_