Fix alignment problems in NEON Sk4b.

Fix alignment problems in NEON Sk4b.

As written at head, the compiler can assume these loads and stores are 4
byte aligned [1].  We want Sk4b to load from any 1-byte aligned address,
to prevent crashes like [2].

[1] https://llvm.org/bugs/show_bug.cgi?id=24421
[2] https://luci-milo.appspot.com/swarming/task/304079e125b1b910/steps/nanobench/0/stdout

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2183133002
CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Committed: https://skia.googlesource.com/skia/+/a5e1e33d3916cf766f876d3def88afb373440a04

[mtklein_C, 2016-07-26 16:22:58]

Description was changed from

==========
Fix alignment problems in NEON Sk4b.

As written at head, the compiler can assume these loads and stores are 4
byte aligned [1].  We want Sk4b to load from any 1-byte aligned address,
to prevent crashes like [2].

[1] https://llvm.org/bugs/show_bug.cgi?id=24421
[2]
https://luci-milo.appspot.com/swarming/task/304079e125b1b910/steps/nanobench/...

BUG=skia:
==========

to

==========
Fix alignment problems in NEON Sk4b.

As written at head, the compiler can assume these loads and stores are 4
byte aligned [1].  We want Sk4b to load from any 1-byte aligned address,
to prevent crashes like [2].

[1] https://llvm.org/bugs/show_bug.cgi?id=24421
[2]
https://luci-milo.appspot.com/swarming/task/304079e125b1b910/steps/nanobench/...

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2183133002
CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot
==========

[mtklein_C, 2016-07-26 16:26:12]

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

[commit-bot: I haz the power, 2016-07-26 16:26:20]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[mtklein_C, 2016-07-26 16:35:27]

The CQ bit was unchecked by mtklein@chromium.org

[mtklein_C, 2016-07-26 16:36:04]

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

[mtklein_C, 2016-07-26 16:36:04]

This has been waiting to strike for months.

[mtklein_C, 2016-07-26 16:36:13]

The CQ bit was checked by mtklein@chromium.org

[commit-bot: I haz the power, 2016-07-26 16:36:21]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[msarett, 2016-07-26 17:06:29]

lgtm

[commit-bot: I haz the power, 2016-07-26 17:07:37]

Description was changed from

==========
Fix alignment problems in NEON Sk4b.

As written at head, the compiler can assume these loads and stores are 4
byte aligned [1].  We want Sk4b to load from any 1-byte aligned address,
to prevent crashes like [2].

[1] https://llvm.org/bugs/show_bug.cgi?id=24421
[2]
https://luci-milo.appspot.com/swarming/task/304079e125b1b910/steps/nanobench/...

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2183133002
CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot
==========

to

==========
Fix alignment problems in NEON Sk4b.

As written at head, the compiler can assume these loads and stores are 4
byte aligned [1].  We want Sk4b to load from any 1-byte aligned address,
to prevent crashes like [2].

[1] https://llvm.org/bugs/show_bug.cgi?id=24421
[2]
https://luci-milo.appspot.com/swarming/task/304079e125b1b910/steps/nanobench/...

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2183133002
CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Committed:
https://skia.googlesource.com/skia/+/a5e1e33d3916cf766f876d3def88afb373440a04
==========

[commit-bot: I haz the power, 2016-07-26 17:07:38]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/a5e1e33d3916cf766f876d3def88afb373440a04