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

core/fpdfapi/fpdf_parser/cpdf_parser.cpp

Index: core/fpdfapi/fpdf_parser/cpdf_parser.cpp
diff --git a/core/fpdfapi/fpdf_parser/cpdf_parser.cpp b/core/fpdfapi/fpdf_parser/cpdf_parser.cpp
index 1af2bd148267f4f8eadf15763217a1fbb625c9ed..de3b68a81aab341e31765d99c226b2c184ca7845 100644
--- a/core/fpdfapi/fpdf_parser/cpdf_parser.cpp
+++ b/core/fpdfapi/fpdf_parser/cpdf_parser.cpp
@@ -618,7 +618,8 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
     bool bOverFlow = false;
     uint32_t size =
         std::min((uint32_t)(m_pSyntax->m_FileLen - pos), kBufferSize);
-    if (!m_pSyntax->m_pFileAccess->ReadBlock(buffer.data(), pos, size))
+    if (m_pSyntax->m_pFileAccess->ReadBlock(buffer.data(), pos, size) != size &&
+        !m_pSyntax->m_pFileAccess->IsEOF())
       break;
 
     for (uint32_t i = 0; i < size; i++) {