Try again to put SkXfermode_opts in SK_OPTS_NS

Try again to put SkXfermode_opts in SK_OPTS_NS

Remember failed attempt https://codereview.chromium.org/1286093004/ ?  I think this one is simpler and safer and even technically legal C++.

BUG=skia:4117
Committed: https://skia.googlesource.com/skia/+/08f9234eaafcda33ebf5e74ec27ca72f4abda4fb

[mtklein_C, 2015-08-18 19:12:07]

The CQ bit was checked by mtklein@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-08-18 19:12:21]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1296183004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1296183004/20001

[mtklein_C, 2015-08-18 19:14:10]

mtklein@chromium.org changed reviewers:
+ djsollen@google.com

[commit-bot: I haz the power, 2015-08-18 19:18:50]

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

[commit-bot: I haz the power, 2015-08-18 19:18:50]

Dry run: This issue passed the CQ dry run.

[djsollen, 2015-08-18 19:22:10]

lgtm

[mtklein_C, 2015-08-18 19:22:54]

The CQ bit was checked by mtklein@chromium.org

[commit-bot: I haz the power, 2015-08-18 19:23:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1296183004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1296183004/20001

[commit-bot: I haz the power, 2015-08-18 19:23:30]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/08f9234eaafcda33ebf5e74ec27ca72f4abda4fb