Roll src/third_party/pdfium d28c5fe2b8b8..6c23cd33e6fe (4 commits)

https://pdfium.googlesource.com/pdfium.git/+log/d28c5fe2b8b8..6c23cd33e6fe

git log d28c5fe2b8b8..6c23cd33e6fe --date=short --first-parent --format='%ad %ae %s'
2020-02-05 brucedawson@chromium.org Fix duplicate header file entry
2020-02-05 brianosman@google.com Stop using Skia's specialized min/max functions
2020-02-05 tsepez@chromium.org Remove stray CJX_Object::InstanceManager_{Set,Move}Instances() decls.
2020-02-05 tsepez@chromium.org Cover CJX_InstanceManager methods from javascript tests.

Created with:
  gclient setdep -r src/third_party/pdfium@6c23cd33e6fe

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: chromium:1048779
Tbr: pdfium-deps-rolls@chromium.org
Change-Id: I1ce1dfa948cd87e8332e014d4bdeae98d888c935
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2040015Reviewed-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@{#738757}

DEPS

@@ -196,7 +196,7 @@ 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': 'd28c5fe2b8b8084c5e9ac3753b10ae786b734b62',
+  'pdfium_revision': '6c23cd33e6fe27335f7ac6c83b87ffdf9184593e',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.