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

core/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp

Index: core/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
diff --git a/core/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp b/core/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
index a9f20a9093b0402580d0b14353fadcec1b591577..0c16ba52bb0e259fcb8ce8fdbf1f04dd0e13c7dd 100644
--- a/core/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
+++ b/core/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
@@ -72,7 +72,7 @@ int32_t GetHeaderOffset(IFX_FileRead* pFile) {
   const size_t kBufSize = 4;
   uint8_t buf[kBufSize];
   for (int32_t offset = 0; offset <= 1024; ++offset) {
-    if (!pFile->ReadBlock(buf, offset, kBufSize))
+    if (pFile->ReadBlock(buf, offset, kBufSize) != kBufSize && !pFile->IsEOF())
       return -1;
 
     if (memcmp(buf, "%PDF", 4) == 0)