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

xfa/fde/xml/cfx_saxreader.cpp

Index: xfa/fde/xml/cfx_saxreader.cpp
diff --git a/xfa/fde/xml/cfx_saxreader.cpp b/xfa/fde/xml/cfx_saxreader.cpp
index b4d48d29379436c2db2e95a514cb7836fa4e8638..313f2d213a5f968f502c0ff993b34720ed3b2e5b 100644
--- a/xfa/fde/xml/cfx_saxreader.cpp
+++ b/xfa/fde/xml/cfx_saxreader.cpp
@@ -86,7 +86,8 @@ bool CFX_SAXFile::StartFile(IFX_SeekableReadStream* pFile,
   }
   m_dwBufSize = std::min(dwLen, kSaxFileBufSize);
   m_pBuf = FX_Alloc(uint8_t, m_dwBufSize);
-  if (!pFile->ReadBlock(m_pBuf, dwStart, m_dwBufSize)) {
+  if (pFile->ReadBlock(m_pBuf, dwStart, m_dwBufSize) != m_dwBufSize &&
+      !pFile->IsEOF()) {
     return false;
   }
   m_dwStart = dwStart;
@@ -104,7 +105,8 @@ bool CFX_SAXFile::ReadNextBlock() {
     return false;
   }
   m_dwBufSize = std::min(dwSize, kSaxFileBufSize);
-  if (!m_pFile->ReadBlock(m_pBuf, m_dwCur, m_dwBufSize)) {
+  if (m_pFile->ReadBlock(m_pBuf, m_dwCur, m_dwBufSize) != m_dwBufSize &&
+      !m_pFile->IsEOF()) {
     return false;
   }
   m_dwBufIndex = 0;