Make SkImageDecoder_libpng be compilable with Chromium libpng

Make SkImageDecoder_libpng be compilable with Chromium libpng

Chromium has libpng with pngusr.h that disables certain functionality with
defines. Use those defines when compiling SkImageDecoder_libpng.cpp.

This makes it possible to use Skia PNG decoder and encoder when compiling dm
with Chromium. Skia PNG decoder and encoder of course is not compiled to the
skia library, but to dm with Chromium.

BUG=skia:2992
Committed: https://skia.googlesource.com/skia/+/93b255b19e01a0f10ac3b9e20f2d8fedcb5e57ca

[Kimmo Kinnunen, 2014-10-16 11:25:03]

kkinnunen@nvidia.com changed reviewers:
+ scroggo@google.com

[scroggo, 2014-10-16 14:14:36]

https://codereview.chromium.org/645883004/diff/1/src/images/SkImageDecoder_li...
File src/images/SkImageDecoder_libpng.cpp (right):

https://codereview.chromium.org/645883004/diff/1/src/images/SkImageDecoder_li...
src/images/SkImageDecoder_libpng.cpp:502: #if PNG_sBIT_SUPPORTED
ifdef*

[Kimmo Kinnunen, 2014-10-17 05:28:01]

On 2014/10/16 14:14:36, scroggo wrote:
>
https://codereview.chromium.org/645883004/diff/1/src/images/SkImageDecoder_li...
> File src/images/SkImageDecoder_libpng.cpp (right):
> 
>
https://codereview.chromium.org/645883004/diff/1/src/images/SkImageDecoder_li...
> src/images/SkImageDecoder_libpng.cpp:502: #if PNG_sBIT_SUPPORTED
> ifdef*

done

[scroggo, 2014-10-17 14:08:50]

lgtm

[Kimmo Kinnunen, 2014-10-20 05:00:34]

The CQ bit was checked by kkinnunen@nvidia.com

[commit-bot: I haz the power, 2014-10-20 05:01:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/645883004/20001

[commit-bot: I haz the power, 2014-10-20 05:07:29]

Committed patchset #2 (id:20001) as 93b255b19e01a0f10ac3b9e20f2d8fedcb5e57ca