Roll src/third_party/pdfium a451858403a2..dc397e0a03e0 (2 commits)

https://pdfium.googlesource.com/pdfium.git/+log/a451858403a2..dc397e0a03e0

git log a451858403a2..dc397e0a03e0 --date=short --first-parent --format='%ad %ae %s'
2020-02-01 tsepez@chromium.org Remove CPDFSDK_Widget::GetAlternateName()
2020-02-01 tsepez@chromium.org Remove GetPDFUnssuportInto().

Created with:
  gclient setdep -r src/third_party/pdfium@dc397e0a03e0

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: Ia952267417bc4a14c70ba4fcb955f88315de2944
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2033951Reviewed-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@{#737565}

DEPS

@@ -197,7 +197,7 @@ 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': 'a451858403a2ff5e9302980cbf813455ec05ef7b',
+  'pdfium_revision': 'dc397e0a03e0a1f36b50bcc25ded030716387d4c',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.