Roll src/third_party/pdfium 270946946c93..b198c7757765 (3 commits)

https://pdfium.googlesource.com/pdfium.git/+log/270946946c93..b198c7757765

git log 270946946c93..b198c7757765 --date=short --first-parent --format='%ad %ae %s'
2019-12-05 tsepez@chromium.org Provide a FPDF_LoadXFA() stub even when XFA not present.
2019-12-05 thestig@chromium.org Fix some nits in parser crypto code.
2019-12-04 asweintraub@google.com Add Apache license to PDFium LICENSE file.

Created with:
  gclient setdep -r src/third_party/pdfium@b198c7757765

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/pdfium-autoroll
Please CC pdfium-deps-rolls@chromium.org on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

Bug: None
Tbr: pdfium-deps-rolls@chromium.org
Change-Id: Ie5f2fa6d521b92db15a1b76f756f52dfd92981be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1952190Reviewed-by: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#721849}

DEPS

@@ -192,7 +192,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling PDFium
   # and whatever else without interference from each other.
-  'pdfium_revision': '270946946c93b5dcc33b24263cee3814f00f6e34',
+  'pdfium_revision': 'b198c775776579910c370e4c6031fa6e9f62ab4e',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.