Roll src/third_party/pdfium 9346b7c0ed1a..77141ccf844b (3 commits)

https://pdfium.googlesource.com/pdfium.git/+log/9346b7c0ed1a..77141ccf844b

git log 9346b7c0ed1a..77141ccf844b --date=short --first-parent --format='%ad %ae %s'
2020-01-09 tsepez@chromium.org Remove unused CXFA_FFWidgetHandler::CreateWidget().
2020-01-09 tsepez@chromium.org Remove two impossible null-argument checks in CPDFSDK_PageView.
2020-01-09 tsepez@chromium.org Remove XFA_TRAVERSEWAY_* definitions

Created with:
  gclient setdep -r src/third_party/pdfium@77141ccf844b

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: Ia78d6ec3e61856bb54c295626d2c27d9e40c7a26
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1994405Reviewed-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@{#730026}

DEPS

@@ -201,7 +201,7 @@ 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': '9346b7c0ed1a2adbb1c25095822cdfc08dbfa0c0',
+  'pdfium_revision': '77141ccf844b5c5ab1deb5c03d873b03ae13b03f',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.