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

core/fxcrt/include/fx_stream.h

Index: core/fxcrt/include/fx_stream.h
diff --git a/core/fxcrt/include/fx_stream.h b/core/fxcrt/include/fx_stream.h
index a91b59f2856c0ccf80fee579b2c2a5e5fb658443..678e30a6ac641c662f9acadf9a4a16592b8e9149 100644
--- a/core/fxcrt/include/fx_stream.h
+++ b/core/fxcrt/include/fx_stream.h
@@ -83,11 +83,11 @@ class IFX_FileRead : public IFX_StreamRead {
  public:
   // IFX_StreamRead:
   void Release() override = 0;
-  FX_BOOL IsEOF() override;
+  FX_BOOL IsEOF() override = 0;
   FX_FILESIZE GetPosition() override;
   size_t ReadBlock(void* buffer, size_t size) override;
 
-  virtual FX_BOOL ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) = 0;
+  virtual size_t ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) = 0;
   virtual FX_FILESIZE GetSize() = 0;
 };
 
@@ -103,7 +103,7 @@ class IFX_FileStream : public IFX_FileRead, public IFX_FileWrite {
   FX_BOOL IsEOF() override = 0;
   FX_FILESIZE GetPosition() override = 0;
   size_t ReadBlock(void* buffer, size_t size) override = 0;
-  FX_BOOL ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) override = 0;
+  size_t ReadBlock(void* buffer, FX_FILESIZE offset, size_t size) override = 0;
   FX_FILESIZE GetSize() override = 0;
 
   // IFX_FileWrite: