Remove unused code.

core/fxcodec/include/fx_codec_flate.h

-// Copyright 2015 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_INCLUDE_FX_CODEC_FLATE_H_
-#define CORE_FXCODEC_INCLUDE_FX_CODEC_FLATE_H_
-
-#include "third_party/zlib_v128/zlib.h"
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-// Note: Some of these return Z_* status codes from zlib.h.
-void* FPDFAPI_FlateInit(void* (*alloc_func)(void*, unsigned int, unsigned int),
-                        void (*free_func)(void*, void*));
-void FPDFAPI_FlateInput(void* context,
-                        const unsigned char* src_buf,
-                        unsigned int src_size);
-int FPDFAPI_FlateOutput(void* context,
-                        unsigned char* dest_buf,
-                        unsigned int dest_size);
-int FPDFAPI_FlateGetAvailIn(void* context);
-int FPDFAPI_FlateGetAvailOut(void* context);
-void FPDFAPI_FlateEnd(void* context);
-
-#ifdef __cplusplus
-}  // extern "C"
-#endif
-
-#endif  // CORE_FXCODEC_INCLUDE_FX_CODEC_FLATE_H_