Fix XFA build after combining PDFium into Chromium binary.

R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/889253003

1 files changed, 3 insertions, 0 deletions

diff --git a/BUILD.gn b/BUILD.gn
index 2ff4938696..0d26287d7b 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -19,6 +19,9 @@ config("pdfium_config") {
     "_FPDFSDK_LIB",
     "_NO_GDIPLUS_",  # workaround text rendering issues on Windows
     "OPJ_STATIC",
+    "PNG_PREFIX",
+    "PNGPREFIX_H",
+    "PNG_USE_READ_MACROS",
   ]
 
   if (pdf_use_skia) {