Revert of Roll PDFium 32b639d..a76a6d8 (patchset #1 id:1 of https://codereview.chromium.org/1592013002/ )

      Reason for revert:
Breaks the 64-bit clang/win bots (see comment 12 on the original CL), Lei is away this week, and the pdfium xfa branch situation is in flux enough that I'm not sure how to fix this myself.

Original issue's description:
> Roll PDFium 32b639d..a76a6d8
>
> https://pdfium.googlesource.com/pdfium.git/+log/32b639d..a76a6d8
>
> BUG=571480
> TBR=ochang@chromium.org
>
> Committed: https://crrev.com/933a299a284ec32ebc43c28a2ee7086f73deb3c1
> Cr-Commit-Position: refs/heads/master@{#369947}

TBR=ochang@chromium.org,thestig@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=571480

Review URL: https://codereview.chromium.org/1601243002

Cr-Commit-Position: refs/heads/master@{#370129}