refactor I420AlphaToABGR to use I420AlphaToARGB internally

refactor I420AlphaToABGR to use I420AlphaToARGB internally

swap U and V and transpose conversion matrix, so I420AlphaToARGB and
I420AlphaToABGR share low level code.

Having less code with same performance allows more focused
optimization for future ARM versions.


R=harryjin@google.com
TBR=harryjin@chromium.org
BUG=libyuv:473, libyuv:516
Committed: https://chromium.googlesource.com/libyuv/libyuv/+/b86dbf24d30308aafca025018f13fc106c36e55b

[fbarchard, 2015-10-27 18:11:34]

Description was changed from

==========
refactor I420AlphaToABGR to use I420AlphaToARGB internally

swap U and V and transpose conversion matrix, so I420AlphaToARGB and
I420AlphaToABGR share low level code.

R=xhwang@chromium.org
BUG=libyuv:473
==========

to

==========
refactor I420AlphaToABGR to use I420AlphaToARGB internally

swap U and V and transpose conversion matrix, so I420AlphaToARGB and
I420AlphaToABGR share low level code.

Having less code with same performance allows more focused
optimization for future ARM versions.


TBR=harryjin@chromium.org
BUG=libyuv:473,libyuv:516
==========

[fbarchard, 2015-10-27 18:11:34]

fbarchard@chromium.org changed reviewers:
+ harryjin@chromium.org
- xhwang@chromium.org

[fbarchard, 2015-10-27 18:19:31]

Windows 32 bit performance
I420AlphaToARGB_Any (616 ms)
I420AlphaToARGB_Unaligned (514 ms)
I420AlphaToARGB_Invert (492 ms)
I420AlphaToARGB_Opt (496 ms)
I420AlphaToARGB_Premult (880 ms)
I420AlphaToABGR_Any (539 ms)
I420AlphaToABGR_Unaligned (515 ms)
I420AlphaToABGR_Invert (483 ms)
I420AlphaToABGR_Opt (488 ms)
I420AlphaToABGR_Premult (849 ms)

Win64
I420AlphaToABGR_Premult (2624 ms)
I420AlphaToARGB_Premult (2618 ms)
I420AlphaToARGB_Any (623 ms)
I420AlphaToABGR_Any (498 ms)
I420AlphaToARGB_Unaligned (479 ms)
I420AlphaToABGR_Unaligned (476 ms)
I420AlphaToARGB_Invert (458 ms)
I420AlphaToARGB_Opt (454 ms)
I420AlphaToABGR_Opt (453 ms)
I420AlphaToABGR_Invert (451 ms)

[harryjin, 2015-10-27 20:36:52]

harryjin@google.com changed reviewers:
+ harryjin@google.com

[harryjin, 2015-10-27 20:36:53]

lgtm

[fbarchard1, 2015-10-27 21:17:27]

Committed patchset #1 (id:1) manually as
b86dbf24d30308aafca025018f13fc106c36e55b (presubmit successful).