Merge to XFA: Separate agg-authored code from fx-authored code.

Original Review URL: https://codereview.chromium.org/1152743007.
BUG=pdfium:166
R=brucedawson@chromium.org, thestig@chromium.org
TBR=brucedawson@chromium.org, thestig@chromium.org

Review URL: https://codereview.chromium.org/1186423003.
54 files changed