Roll src/third_party/pdfium 5540fdbe7451..55cc5f2199b1 (7 commits)

https://pdfium.googlesource.com/pdfium.git/+log/5540fdbe7451..55cc5f2199b1

git log 5540fdbe7451..55cc5f2199b1 --date=short --first-parent --format='%ad %ae %s'
2020-04-06 tsepez@chromium.org Move uint8_t vectors to data partition in xfa/
2020-04-06 tsepez@chromium.org Move uint8_t vectors to data partition in fxjs/
2020-04-06 tsepez@chromium.org Put uint8_t vectors into data partition in fpdfsdk/
2020-04-06 tsepez@chromium.org Put uint8_t vectors into the Data partition in fpdfapi/
2020-04-06 thestig@chromium.org Fix regression in FPDF_CountNamedDests().
2020-04-06 thestig@chromium.org Add more tests for FPDF_CountNamedDests().
2020-04-06 thestig@chromium.org Fix typos in some .in files and regenerate the .pdf files.

Created with:
  gclient setdep -r src/third_party/pdfium@55cc5f2199b1

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: I85b9bb34d3abe405ae35d672c27ac0b2343a2131
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2138968Reviewed-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@{#756969}

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': '5540fdbe74510620b27fc3cc29a720e766584189',
+  'pdfium_revision': '55cc5f2199b1f074c36019a7dd7e70223994eb30',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.