XFA: Fix the Mac build after commit 375a86403b7f.

TBR=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1578003002 .

1 files changed, 3 insertions, 2 deletions

diff --git a/xfa/src/fgas/src/crt/fx_stream.cpp b/xfa/src/fgas/src/crt/fx_stream.cpp
index fb8c3c7fba..9663351602 100644
--- a/xfa/src/fgas/src/crt/fx_stream.cpp
+++ b/xfa/src/fgas/src/crt/fx_stream.cpp
@@ -1323,8 +1323,9 @@ FX_BOOL CFX_BufferAccImp::ReadBlock(void* buffer,
     return FALSE;

   }

   const uint8_t* pBuffer = m_pBufferRead->GetBlockBuffer();

-  FX_FILESIZE dwOffset = offset - dwBlockOffset;

-  size_t dwCopySize = std::min(size, dwBlockSize - dwOffset);

+  const FX_FILESIZE dwOffset = offset - dwBlockOffset;

+  size_t dwCopySize =

+      std::min(size, static_cast<size_t>(dwBlockSize - dwOffset));

   FXSYS_memcpy(buffer, pBuffer + dwOffset, dwCopySize);

   offset = dwCopySize;

   size -= dwCopySize;