in the attempt to fix 627393, changed IFX_FileRead's readBlock to return the length it reads

xfa/fxfa/xfa_ffapp.h

Index: xfa/fxfa/xfa_ffapp.h
diff --git a/xfa/fxfa/xfa_ffapp.h b/xfa/fxfa/xfa_ffapp.h
index 359f8ffa3cf680e7239c0f16f655dfe4348ca630..b718f07d6bbb1dc0656105d8ad2022550b7dc3a8 100644
--- a/xfa/fxfa/xfa_ffapp.h
+++ b/xfa/fxfa/xfa_ffapp.h
@@ -29,13 +29,16 @@ class CXFA_FileRead : public IFX_SeekableReadStream {
   explicit CXFA_FileRead(const std::vector<CPDF_Stream*>& streams);
   ~CXFA_FileRead() override;
 
-  // IFX_SeekableReadStream
+  // IFX_FileRead
+  bool IsEOF() override;
   FX_FILESIZE GetSize() override;
-  bool ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) override;
+  size_t ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) override;
   void Release() override;
 
  protected:
   CFX_ObjectArray<CPDF_StreamAcc> m_Data;
+  FX_FILESIZE m_FileSize;
+  FX_FILESIZE m_nCurPos;
 };
 
 class CXFA_FFApp {