4-at-a-time SkPMColor -> SkPMFloat API.

4-at-a-time SkPMColor -> SkPMFloat API.

Please see if this looks usable.  It may even give a perf boost if you use it, even without custom implementations for each instruction set.

I've been trying this morning to beat this naive loop implementation, but so far no luck with either _SSE2.h or _SSSE3.h.  It's possible this is an artifact of the microbenchmark, because we're not doing anything between the conversions.  I'd like to see how this fits into real code, what assembly's generated, what the hot spots are, etc.

I've updated the tests to test these new APIs, and splintered off a pair of new benchmarks that use the new APIs.  This required some minor rejiggering in the benches.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/548bf38b28986fab6770350b72247d7114d98184

[mtklein_C, 2015-03-05 19:08:41]

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

[reed1, 2015-03-05 19:22:44]

Looks usable. lgtm

bikeshed : From4PMColors, etc.? I think I'd like the name to some how reflect
the number of entries. 4? quad?

[mtklein, 2015-03-05 19:25:23]

On 2015/03/05 19:22:44, reed1 wrote:
> Looks usable. lgtm
> 
> bikeshed : From4PMColors, etc.? I think I'd like the name to some how reflect
> the number of entries. 4? quad?

Went with {From,To,ClampTo}4PMColors.

[mtklein, 2015-03-05 19:26:03]

The CQ bit was checked by mtklein@google.com

[mtklein, 2015-03-05 19:26:03]

The patchset sent to the CQ was uploaded after l-g-t-m from reed@google.com
Link to the patchset: https://codereview.chromium.org/978213003/#ps100001
(title: "4")

[commit-bot: I haz the power, 2015-03-05 19:26:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/978213003/100001

[commit-bot: I haz the power, 2015-03-05 19:32:03]

Committed patchset #6 (id:100001) as
https://skia.googlesource.com/skia/+/548bf38b28986fab6770350b72247d7114d98184