Roll src/third_party/pdfium 2dd3f0f2c0f7..a8817db1767d (4 commits)

https://pdfium.googlesource.com/pdfium.git/+log/2dd3f0f2c0f7..a8817db1767d

git log 2dd3f0f2c0f7..a8817db1767d --date=short --first-parent --format='%ad %ae %s'
2020-04-16 thestig@chromium.org Use more spans in CBC_PDF417HighLevelEncoder.
2020-04-16 dhoss@chromium.org Restyle listbox_form.pdf and rename multiselect form field
2020-04-16 tsepez@chromium.org Move scalar vectors to data partition in fxbarcode/
2020-04-16 tsepez@chromium.org Move scalar vectors to data partition in fxge/win32

Created with:
  gclient setdep -r src/third_party/pdfium@a8817db1767d

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: I40c40db0630e5fb5f83643021405d171729c968c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2153637Reviewed-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@{#759835}

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': '2dd3f0f2c0f770992b580d848a5cbaabe649cb77',
+  'pdfium_revision': 'a8817db1767dbe6f79782ff00335d819afe296e9',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.