Revert of Remove the document tagged code as it is unused.

Revert of Remove the document tagged code as it is unused. (patchset #2 id:20001 of https://codereview.chromium.org/2188213002/ )

Reason for revert:
Code being used by Android foxit viewer

Original issue's description:
> Remove the document tagged code as it is unused.
> 
> The fpdf_tagged.h, tagged_int.h and doc_tagged.cpp code is currently unused
> and can be removed.
> 
> Committed: https://pdfium.googlesource.com/pdfium/+/dbfc3522a6ee24d17f2c50a5dcc465db52a280ee

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

[npm, 2016-08-26 16:55:17]

The CQ bit was checked by npm@chromium.org

[npm, 2016-08-26 16:55:17]

Created Revert of Remove the document tagged code as it is unused.

[commit-bot: I haz the power, 2016-08-26 16:55:25]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-26 16:56:34]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-08-26 16:56:35]

Try jobs failed on following builders:
  linux_no_v8 on master.tryserver.client.pdfium (JOB_FAILED,
https://build.chromium.org/p/tryserver.client.pdfium/builders/linux_no_v8/bui...)
  linux_xfa on master.tryserver.client.pdfium (JOB_FAILED,
https://build.chromium.org/p/tryserver.client.pdfium/builders/linux_xfa/build...)

[npm, 2016-08-26 17:28:07]

Description was changed from

==========
Revert of Remove the document tagged code as it is unused. (patchset #2 id:20001
of https://codereview.chromium.org/2188213002/ )

Reason for revert:
Code being used by Android foxit viewer

Original issue's description:
> Remove the document tagged code as it is unused.
> 
> The fpdf_tagged.h, tagged_int.h and doc_tagged.cpp code is currently unused
> and can be removed.
> 
> Committed:
https://pdfium.googlesource.com/pdfium/+/dbfc3522a6ee24d17f2c50a5dcc465db52a2...

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

to

==========
Revert of Remove the document tagged code as it is unused. (patchset #2 id:20001
of https://codereview.chromium.org/2188213002/ )

Reason for revert:
Code being used by Android foxit viewer

Original issue's description:
> Remove the document tagged code as it is unused.
> 
> The fpdf_tagged.h, tagged_int.h and doc_tagged.cpp code is currently unused
> and can be removed.
> 
> Committed:
https://pdfium.googlesource.com/pdfium/+/dbfc3522a6ee24d17f2c50a5dcc465db52a2...

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

[npm, 2016-08-26 17:34:27]

Closing and doing revert on Issue 2281083002