Fix ALL the include guards.

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 _FX_CODEC_H_
-#define _FX_CODEC_H_
-#ifndef _FXCRT_EXTENSION_
+#ifndef FX_CODEC_H_
+#define FX_CODEC_H_
+
 #include "../fxcrt/fx_ext.h"
-#endif
 #include "fx_codec_def.h"
 #include "fx_codec_provider.h"
+
 class CFX_DIBSource;
 class ICodec_ScanlineDecoder;
 class ICodec_BasicModule;
 class ICodec_FaxModule;
 class ICodec_JpegModule;
 class ICodec_JpxModule;
 class ICodec_Jbig2Module;
 class ICodec_IccModule;
 class ICodec_FlateModule;
 class ICodec_Jbig2Encoder;
@@ skipping 255 matching lines @@
     virtual void                        DestroyTransform(FX_LPVOID pTransform) = 0;
 
     virtual void                        Translate(FX_LPVOID pTransform, FX_FLOAT* pSrcValues, FX_FLOAT* pDestValues) = 0;
 
     virtual void                        TranslateScanline(FX_LPVOID pTransform, FX_LPBYTE pDest, FX_LPCBYTE pSrc, int pixels) = 0;
     virtual void                        SetComponents(FX_DWORD nComponents) = 0;
 };
 void AdobeCMYK_to_sRGB(FX_FLOAT c, FX_FLOAT m, FX_FLOAT y, FX_FLOAT k, FX_FLOAT& R, FX_FLOAT& G, FX_FLOAT& B);
 void AdobeCMYK_to_sRGB1(FX_BYTE c, FX_BYTE m, FX_BYTE y, FX_BYTE k, FX_BYTE& R, FX_BYTE& G, FX_BYTE& B);
 FX_BOOL MD5ComputeID(FX_LPCVOID buf, FX_DWORD dwSize, FX_BYTE ID[16]);
-#endif
+
+#endif  // FX_CODEC_H_