Roll PDFium from daef088d069f to e21911cc1c77 (11 revisions)

https://pdfium.googlesource.com/pdfium.git/+log/daef088d069f..e21911cc1c77

2020-10-09 tsepez@chromium.org Make _TIFFBuiltinCODECS be const data.
2020-10-09 thestig@chromium.org Simplify struct TbConvertAdditional.
2020-10-09 thestig@chromium.org Avoid relocations in struct BarCodeInfo.
2020-10-09 tsepez@chromium.org Add pdfium::span::front() and back()
2020-10-09 tsepez@chromium.org Move CFXA_MapModule to CFXJSE_MapModule and add tests
2020-10-09 nigi@chromium.org Disable some Windows-only embedder tests which fail with Skia/SkiaPaths.
2020-10-09 nigi@chromium.org Update Skia/SkiaPaths embedder tests' macOS expected results.
2020-10-08 tsepez@chromium.org Move XFA_ATTRIBUTE_CALLBACK from fxjs/ to xfa/ directory
2020-10-08 tsepez@chromium.org Add some missing const in CFXJSE_Context
2020-10-08 tsepez@chromium.org Completely re-implement CFXA_MapModule data storage
2020-10-08 thestig@chromium.org Make more XFA attribute data truly read-only.

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/+doc/master/autoroll/README.md

Bug: None
Tbr: pdfium-deps-rolls@chromium.org
Change-Id: I49f4770debd38906e694eab2014de1aab0e63575
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2463791Reviewed-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@{#815864}

DEPS

@@ -215,7 +215,7 @@ 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': 'daef088d069f8d49d8ba668f475dd21ca0e5c087',
+  'pdfium_revision': 'e21911cc1c77d39dbc51001845bbfce2783e6514',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.