Revert of Roll PDFium 32b639d..76c9957 (patchset #1 id:1 of https://codereview.chromium.org/1591173002/ )

      Reason for revert:
Breaks building 'all': https://build.chromium.org/p/chromium.fyi/builders/CrWinClang%28shared%29/builds/7023/steps/compile/logs/stdio

FAILED: ninja -t msvc -e environment.x86 -- &quot..\..\third_party/llvm-build/Release+Asserts/bin/clang-cl&quot -m32 /nologo /showIncludes /FC @obj\third_party\pdfium\samples\pdfium_diff.image_diff_png.obj.rsp /c ..\..\third_party\pdfium\samples\image_diff_png.cc /Foobj\third_party\pdfium\samples\pdfium_diff.image_diff_png.obj /Fdobj\third_party\pdfium\samples\pdfium_diff.cc.pdb
In file included from ..\..\third_party\pdfium\samples\image_diff_png.cc:20:
..\..\third_party/libpng/png.h(317,10) :  fatal error: 'zlib.h' file not found
#include &quotzlib.h&quot
         ^
1 error generated.

Original issue's description:
> Roll PDFium 32b639d..76c9957
>
> https://pdfium.googlesource.com/pdfium.git/+log/32b639d..76c9957
>
> BUG=571480
> TBR=thestig@chromium.org
>
> Committed: https://crrev.com/081755d258fa6c2ab7f2338fb008c4cbdf1cf884
> Cr-Commit-Position: refs/heads/master@{#369914}

TBR=thestig@chromium.org,ochang@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=571480

Review URL: https://codereview.chromium.org/1590403004

Cr-Commit-Position: refs/heads/master@{#369926}