Refactor fx_font part 3

core/fxge/include/cfx_fontcache.h

 // Copyright 2016 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_FXGE_INCLUDE_CFX_FONTCACHE_H_
 #define CORE_FXGE_INCLUDE_CFX_FONTCACHE_H_
 
 #include <map>
 
 #include "core/fxcrt/include/fx_system.h"
 #include "core/fxge/include/fx_font.h"
 #include "core/fxge/include/fx_freetype.h"
 
+class CFX_FaceCache;
+
 class CFX_FontCache {
  public:
   CFX_FontCache();
   ~CFX_FontCache();
   CFX_FaceCache* GetCachedFace(CFX_Font* pFont);
   void ReleaseCachedFace(CFX_Font* pFont);
   void FreeCache(FX_BOOL bRelease = FALSE);
 #ifdef _SKIA_SUPPORT_
   CFX_TypeFace* GetDeviceCache(CFX_Font* pFont);
 #endif
 
  private:
   using CFX_FTCacheMap = std::map<FXFT_Face, CFX_CountedFaceCache*>;
   CFX_FTCacheMap m_FTFaceMap;
   CFX_FTCacheMap m_ExtFaceMap;
 };
 
 #endif  // CORE_FXGE_INCLUDE_CFX_FONTCACHE_H_