Restore old NEON blit_mask_d32_a8 methods.

Restore old NEON blit_mask_d32_a8 methods.

As you'll see from the BUG line, we have a strong indication that the new Sk4px
methods regress some devices.  This restores the old code back as literally as possible
while still fitting in SkOpts framework.

This is ideally temporary breathing room.

We should get an early indication of if those bugs will improve by watching https://perf.skia.org/#4004

BUG=skia:4117, 525844, 519596, 524149
Committed: https://skia.googlesource.com/skia/+/12d40c18b9f624f3a6b674f10a11504fd3ea5642

[mtklein_C, 2015-09-01 17:08:08]

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

[commit-bot: I haz the power, 2015-09-01 17:08:22]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1312763009/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1312763009/1

[mtklein_C, 2015-09-01 17:11:30]

The CQ bit was unchecked by mtklein@chromium.org

[mtklein_C, 2015-09-01 17:13:59]

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

[reed1, 2015-09-01 17:53:40]

lgtm

[mtklein_C, 2015-09-01 18:02:30]

The CQ bit was checked by mtklein@chromium.org

[commit-bot: I haz the power, 2015-09-01 18:02:43]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1312763009/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1312763009/1

[commit-bot: I haz the power, 2015-09-01 18:03:17]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/12d40c18b9f624f3a6b674f10a11504fd3ea5642