Merge to XFA: Allow external font-path configuration from pdfium_test.

TBR=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1268323004 .

(cherry picked from commit 9311163b564785a3a3ccdcb09bd3b7d0b2976d1a)

Review URL: https://codereview.chromium.org/1368513002 .
12 files changed