Fix mac build breakage at ce4ffb8.
Fix mac build breakage at ce4ffb8.

R=thestig@chromium.org

Review URL: https://codereview.chromium.org/1287053006 .

DrAlexx/pdfium,was4444/pdfium,azunite/libpdfium,DrAlexx/pdfium,andoma/pdfium,andoma/pdfium,andoma/pdfium,DrAlexx/pdfium,was4444/pdfium,azunite/libpdfium,was4444/pdfium,andoma/pdfium,DrAlexx/pdfium,was4444/pdfium,azunite/libpdfium,azunite/libpdfium