Roll src/third_party/pdfium dbb6fcdf4353..83d503bc728e (4 commits)

https://pdfium.googlesource.com/pdfium.git/+log/dbb6fcdf4353..83d503bc728e

git log dbb6fcdf4353..83d503bc728e --date=short --first-parent --format='%ad %ae %s'
2020-03-11 thestig@chromium.org Force .evt files to have LF line endings.
2020-03-11 tsepez@chromium.org Convert CFXJSE_FormCalcContext static methods to anon functions
2020-03-11 thestig@chromium.org Make more members const in cxfa_ffpageview.h.
2020-03-11 tsepez@chromium.org Remove indexing in CFXJSE_FormCalcContext::DotAccessorCommon().

Created with:
  gclient setdep -r src/third_party/pdfium@83d503bc728e

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: I384ebbb36561c529b7558c69e08b98fc76ca05ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2100034Reviewed-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@{#749518}

DEPS

@@ -195,7 +195,7 @@ 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': 'dbb6fcdf4353e6f186ee60b377d594c813f8fa63',
+  'pdfium_revision': '83d503bc728e8a42d500727f3982de21c02f406b',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.