fix linux build
fix linux build

Found when adding pdf_use_skia_paths canary
to skia status

R=dsinclair@chromium.org, borenet@google.com
BUG=skia:5849

Review-Url: https://codereview.chromium.org/2569003002

DrAlexx/pdfium,DrAlexx/pdfium,DrAlexx/pdfium,DrAlexx/pdfium