Remove even more const casting from core.

core/fpdfapi/fpdf_font/include/cpdf_font.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_FPDFAPI_FPDF_FONT_INCLUDE_CPDF_FONT_H_
 #define CORE_FPDFAPI_FPDF_FONT_INCLUDE_CPDF_FONT_H_
 
 #include "core/fxcrt/include/fx_string.h"
@@ skipping 53 matching lines @@
   virtual int CountChar(const FX_CHAR* pString, int size) const;
   virtual int AppendChar(FX_CHAR* buf, uint32_t charcode) const;
   virtual int GetCharSize(uint32_t charcode) const;
   virtual int GlyphFromCharCode(uint32_t charcode,
                                 FX_BOOL* pVertGlyph = nullptr);
   virtual int GlyphFromCharCodeExt(uint32_t charcode);
   virtual CFX_WideString UnicodeFromCharCode(uint32_t charcode) const;
   virtual uint32_t CharCodeFromUnicode(FX_WCHAR Unicode) const;
 
   const CFX_ByteString& GetBaseFont() const { return m_BaseFont; }
-  const CFX_SubstFont* GetSubstFont() const { return m_Font.GetSubstFont(); }
+  CFX_SubstFont* GetSubstFont() const { return m_Font.GetSubstFont(); }
   uint32_t GetFlags() const { return m_Flags; }
   FX_BOOL IsEmbedded() const { return IsType3Font() || m_pFontFile != nullptr; }
   CPDF_StreamAcc* GetFontFile() const { return m_pFontFile; }
   CPDF_Dictionary* GetFontDict() const { return m_pFontDict; }
   FX_BOOL IsStandardFont() const;
   FXFT_Face GetFace() const { return m_Font.GetFace(); }
   void AppendChar(CFX_ByteString& str, uint32_t charcode) const;
 
   void GetFontBBox(FX_RECT& rect) const { rect = m_FontBBox; }
   int GetTypeAscent() const { return m_Ascent; }
@@ skipping 34 matching lines @@
   mutable FX_BOOL m_bToUnicodeLoaded;
   int m_Flags;
   FX_RECT m_FontBBox;
   int m_StemV;
   int m_Ascent;
   int m_Descent;
   int m_ItalicAngle;
 };
 
 #endif  // CORE_FPDFAPI_FPDF_FONT_INCLUDE_CPDF_FONT_H_