Merge to XFA: Revert "Revert "Add type cast definitions for CPDF_Reference.""

Merge to XFA: Revert "Revert "Add type cast definitions for CPDF_Reference.""

This reverts commit 7e155865c90cc1115cc7193b7646a341d8f9093e.

Add type cast definitions for CPDF_Reference.

This Cl adds ToReference, CPDF_Object::AsReference and CPDF_Object::IsReference
and updates the src to use them as needed.

BUG=pdfium:201
R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1418923005 .

(cherry picked from commit 6ee3484bcb413f4cce303e237fe15e2bdaf51ade)

Committed: https://pdfium.googlesource.com/pdfium/+/bf81c14cdb2b336a62f97119315f6bc43502e840

[dsinclair, 2015-10-26 20:13:54]

PTAL. Merged with conflict.

https://codereview.chromium.org/1410073007/diff/1/fpdfsdk/src/fpdfppo.cpp
File fpdfsdk/src/fpdfppo.cpp (right):

https://codereview.chromium.org/1410073007/diff/1/fpdfsdk/src/fpdfppo.cpp#new...
fpdfsdk/src/fpdfppo.cpp:220: int newobjnum = GetNewObjId(pDoc, pMapPtrToPtr,
pReference);
There was a merge conflict here because line 220 had changed.

[Tom Sepez, 2015-10-26 20:52:57]

lgtm

[dsinclair, 2015-10-26 20:54:42]

Committed patchset #1 (id:1) manually as
bf81c14cdb2b336a62f97119315f6bc43502e840 (presubmit successful).