Fix the NaCl bitstream reader to report fatal errors.

lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp

Index: lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp
diff --git a/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp b/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp
index d356985c8e51ed97cf536a086969d964243dd464..c1fb4a84aa1e43f69db9317cd7a38470143cc4c1 100644
--- a/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp
+++ b/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp
@@ -1846,10 +1846,12 @@ std::error_code NaClBitcodeReader::InitStreamFromBuffer() {
     return Error(InvalidBitstream,
                  "Bitcode stream should be a multiple of 4 bytes in length");
 
-  if (Header.Read(BufPtr, BufEnd))
+  const unsigned char *HeaderPtr = BufPtr;
+  if (Header.Read(HeaderPtr, BufEnd))
     return Error(InvalidBitstream, Header.Unsupported());
 
-  StreamFile.reset(new NaClBitstreamReader(BufPtr, BufEnd));
+  StreamFile.reset(new NaClBitstreamReader(BufPtr, BufEnd,
+                                           Header.getHeaderSize()));
   Stream.init(StreamFile.get());
 
   if (AcceptHeader())