Roll PDFium from b6525ec96573 to a163e26c8305 (10 revisions)

https://pdfium.googlesource.com/pdfium.git/+log/b6525ec96573..a163e26c8305

2020-09-11 thestig@chromium.org Use CheckedNumerics to calculate size in CalculatePitchAndSize().
2020-09-11 thestig@chromium.org Funnel all CFX_DIBitmap::Create() allocations through FX_TryAlloc().
2020-09-11 thestig@chromium.org Use CheckedNumerics to calculate pitch in CalculatePitchAndSize().
2020-09-10 tsepez@chromium.org Add missing move operators for CFX_BinaryBuf
2020-09-10 thestig@chromium.org Check for potential integer overflows in CFX_DIBitmap::Create().
2020-09-10 tsepez@chromium.org Add missing |const| to CXFA_FMExpression classes
2020-09-10 tsepez@chromium.org Add missing |noexcept| keyword to our move-constructors.
2020-09-10 nigi@chromium.org Enable FPDFFlattenEmbedderTest.BUG_896366 for Skia.
2020-09-10 nigi@chromium.org Fix CPDFSecurityHandlerEmbedderTest.PasswordAfterGenerateSave for Skia.
2020-09-10 tsepez@chromium.org Make CFXA_TextParser a GCed class.

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: chromium:1124660
Tbr: pdfium-deps-rolls@chromium.org
Change-Id: Ic82d1227e3e3f976b4256252a6889f79cee414b7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2405879Reviewed-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@{#806066}

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': 'b6525ec96573078b680538b7c4e12acce59d4574',
+  'pdfium_revision': 'a163e26c830518c9a92c09c7f6011f5b517b20c1',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.