Port SkBlitRow::Color32 to SkOpts.

Port SkBlitRow::Color32 to SkOpts.

This was a pre-SkOpts attempt that we can bring under its wing now.

This should be a perf no-op, deo volente.

BUG=skia:4117
Committed: https://skia.googlesource.com/skia/+/4a37d08382a16717cde52c3d2687b021c5413464

[mtklein, 2015-09-10 00:57:23]

The CQ bit was checked by mtklein@google.com to run a CQ dry run

[commit-bot: I haz the power, 2015-09-10 00:57:36]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1314863006/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1314863006/1

[mtklein_C, 2015-09-10 01:00:13]

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

[commit-bot: I haz the power, 2015-09-10 01:02:32]

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

[commit-bot: I haz the power, 2015-09-10 01:02:33]

Dry run: This issue passed the CQ dry run.

[reed1, 2015-09-10 16:56:46]

lgtm

[mtklein, 2015-09-10 17:37:31]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2015-09-10 17:37:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1314863006/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1314863006/1

[commit-bot: I haz the power, 2015-09-10 17:38:05]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/4a37d08382a16717cde52c3d2687b021c5413464