Make code compile with clang_use_chrome_plugin (part IV)

fpdfsdk/include/fsdk_define.h

Index: fpdfsdk/include/fsdk_define.h
diff --git a/fpdfsdk/include/fsdk_define.h b/fpdfsdk/include/fsdk_define.h
index 4a470206d3df0e1b51672ae92198868d3d172c46..89c3e739a71254dc71c9df4a04c21b149e6bea76 100644
--- a/fpdfsdk/include/fsdk_define.h
+++ b/fpdfsdk/include/fsdk_define.h
@@ -40,12 +40,12 @@ class CPDF_CustomAccess final : public IFX_FileRead {
   ~CPDF_CustomAccess() override {}
 
   // IFX_FileRead
-  FX_FILESIZE GetSize() override { return m_FileAccess.m_FileLen; }
-  void Release() override { delete this; }
+  FX_FILESIZE GetSize() override;
+  void Release() override;
   FX_BOOL ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) override;
 
 #ifdef PDF_ENABLE_XFA
-  virtual CFX_ByteString GetFullPath() { return ""; }
+  virtual CFX_ByteString GetFullPath();
   virtual FX_BOOL GetByte(uint32_t pos, uint8_t& ch);
   virtual FX_BOOL GetBlock(uint32_t pos, uint8_t* pBuf, uint32_t size);
 #endif  // PDF_ENABLE_XFA
@@ -69,7 +69,7 @@ class CFPDF_FileStream : public IFX_FileStream {
   void Release() override;
   FX_FILESIZE GetSize() override;
   FX_BOOL IsEOF() override;
-  FX_FILESIZE GetPosition() override { return m_nCurPos; }
+  FX_FILESIZE GetPosition() override;
   FX_BOOL ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) override;
   size_t ReadBlock(void* buffer, size_t size) override;
   FX_BOOL WriteBlock(const void* buffer,