simplify BlendTest.cpp

simplify BlendTest.cpp

  - streamline the testing down to just byte multiplies
    (that's always where the blend algorithms vary)
  - add another approximate multiply (x*y+255)>>8
  - add another variant of the perfect multiply, ((x*y+128)*257)>>16

I've realized ((x*y+128)*257)>>16 might be just as fast in SSE/NEON 
as our current (x*y+x)>>8 approximation.  Good to be testing it here.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/195fe08421f3a6c52ed621be96dbcc5393b41e69

[mtklein_C, 2015-11-17 15:44:15]

Description was changed from

==========
simplify BlendTest.cpp

  - streamline the testing down to just byte multiplies
    (that's always where the blend algorithms vary)
  - add another variant of the perfect multiply, ((x*y+128)*257)>>16

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

to

==========
simplify BlendTest.cpp

  - streamline the testing down to just byte multiplies
    (that's always where the blend algorithms vary)
  - add another variant of the perfect multiply, ((x*y+128)*257)>>16

I've realized ((x*y+128)*257)>>16 might be just as fast in SSE/NEON 
as our current (x*y+x)>>8 approximation.  Good to be testing it here.

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

[mtklein_C, 2015-11-17 15:46:25]

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

[commit-bot: I haz the power, 2015-11-17 15:46:31]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1453043005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1453043005/1

[mtklein_C, 2015-11-17 15:51:45]

Description was changed from

==========
simplify BlendTest.cpp

  - streamline the testing down to just byte multiplies
    (that's always where the blend algorithms vary)
  - add another variant of the perfect multiply, ((x*y+128)*257)>>16

I've realized ((x*y+128)*257)>>16 might be just as fast in SSE/NEON 
as our current (x*y+x)>>8 approximation.  Good to be testing it here.

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

to

==========
simplify BlendTest.cpp

  - streamline the testing down to just byte multiplies
    (that's always where the blend algorithms vary)
  - add another approximate multiply (x*y+255)>>8
  - add another variant of the perfect multiply, ((x*y+128)*257)>>16

I've realized ((x*y+128)*257)>>16 might be just as fast in SSE/NEON 
as our current (x*y+x)>>8 approximation.  Good to be testing it here.

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

[mtklein_C, 2015-11-17 15:53:06]

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

[commit-bot: I haz the power, 2015-11-17 15:53:10]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1453043005/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1453043005/20001

[mtklein_C, 2015-11-17 15:53:13]

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

[commit-bot: I haz the power, 2015-11-17 16:06:45]

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

[commit-bot: I haz the power, 2015-11-17 16:06:46]

Dry run: This issue passed the CQ dry run.

[reed1, 2015-11-17 16:28:10]

lgtm

[mtklein_C, 2015-11-17 16:38:12]

The CQ bit was checked by mtklein@chromium.org

[commit-bot: I haz the power, 2015-11-17 16:38:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1453043005/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1453043005/20001

[commit-bot: I haz the power, 2015-11-17 16:39:03]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/195fe08421f3a6c52ed621be96dbcc5393b41e69