Cannot be upstreamed as is. It would break upstreams vendored zxing-cpp.

--- a/source/fitz/zxingbarcode.cpp
+++ b/source/fitz/zxingbarcode.cpp
@@ -28,13 +28,13 @@
 #error "FZ_ENABLE_BARCODE set without HAVE_ZXINGCPP!"
 #endif
 
-#include "ReadBarcode.h"
+#include "ZXing/ReadBarcode.h"
 
 #ifdef ZXING_EXPERIMENTAL_API
-#include "WriteBarcode.h"
+#include "ZXing/WriteBarcode.h"
 #else
-#include "BitMatrix.h"
-#include "MultiFormatWriter.h"
+#include "ZXing/BitMatrix.h"
+#include "ZXing/MultiFormatWriter.h"
 #endif
 
 using namespace ZXing;