Revert of Enable XFA-Forms for the PDFium plugin (patchset #1 id:1 of https://codereview.chromium.org/1761673002/ )
Revert of Enable XFA-Forms for the PDFium plugin (patchset #1 id:1 of https://codereview.chromium.org/1761673002/ )

Reason for revert:
Fails to build with clang-cl with very very scary warnings:

In file included from ..\..\third_party\pdfium\xfa/src/fxfa/src/app/xfa_ffapp.h:15:
..\..\third_party\pdfium\xfa/src/fgas/include/fx_fnt.h(131,23) :  error: first operand of this 'memcmp' call is a pointer to dynamic class '_FX_FONTSIGNATURE'; vtable pointer will be compared [-Werror,-Wdynamic-class-memaccess]
         FXSYS_memcmp(&left.FontSignature, &right.FontSignature,
         ~~~~~~~~~~~~ ^
..\..\third_party\pdfium\xfa/src/fgas/include/fx_fnt.h(131,23) :  note: explicitly cast the pointer to silence this warning
         FXSYS_memcmp(&left.FontSignature, &right.FontSignature,
                      ^
                      (void*)

Reverting for now.

Original issue's description:
> Enable XFA-Forms for the PDFium plugin.
>
> This is a change to gather stability, performance, and size
> data and will be rolled back by 2016-03-15.
>
> This is the gyp portion of the change; the GN variables
> controlling the same things currently reside in the pdfium
> product itsef.
>
> Committed: https://crrev.com/afa43e7fa9754cff9ceb6969c665830a79a84c5b
> Cr-Commit-Position: refs/heads/master@{#379622}

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

Review URL: https://codereview.chromium.org/1773043002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#379700}

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