Flip conditionals to positive logic in pdfium_test.
Flip conditionals to positive logic in pdfium_test.

Also merge a check for failed document loads from XFA.

R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1362143002 .

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