Implement support for dual source blending in ES

Implement support for dual source blending in ES

Use EXT_blend_func_extended to implement dual source blending in OpenGL
ES. The extension is the ES version of ARB_blend_func_extended.

The extension provides gl_SecondaryFragColorEXT for ES 2.0 contexts.
The extension provides glBindFragDataLocationIndexed to bind a custom
fragment shader output to the secondary color for ES 3.0 contexts.

For ES 3.1 contexts, the extension would also give
"layout (location=0, index=1)" output varible layout modifier syntax,
but it is not used in this patch.

The extension needs #extension GL_EXT_blend_func_extended : require
directive for the variables to be available in ES 2.0. For ES 3.0, the
directive relaxes the rules for the amount of output variables without
layout location qualifiers.

OpenGL continues to use GL_ARB_blend_func_extended for dual source
blending.

Committed: https://skia.googlesource.com/skia/+/d94708e71e8611015cdeb4f5874a11816e40ecdc

[Kimmo Kinnunen, 2015-07-30 13:11:24]

kkinnunen@nvidia.com changed reviewers:
+ bsalomon@google.com

[Kimmo Kinnunen, 2015-07-30 13:11:25]

Not that critical time-wise, since there's no other driver implementation
available except my command buffer + ANGLE implementation..

OTOH, if you have plenty of free time (which I'm sure you do :) ) or interest,
have a look..

[bsalomon, 2015-07-30 14:07:19]

On 2015/07/30 13:11:25, Kimmo Kinnunen wrote:
> Not that critical time-wise, since there's no other driver implementation
> available except my command buffer + ANGLE implementation..
> 
> OTOH, if you have plenty of free time (which I'm sure you do :) ) or interest,
> have a look..

lgtm, thanks for adding it!

[Kimmo Kinnunen, 2015-07-31 05:38:51]

The CQ bit was checked by kkinnunen@nvidia.com

[commit-bot: I haz the power, 2015-07-31 05:38:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1266773003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1266773003/1

[commit-bot: I haz the power, 2015-07-31 05:47:06]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/d94708e71e8611015cdeb4f5874a11816e40ecdc

[Kimmo Kinnunen, 2015-07-31 12:53:40]

So this fails Test-Android-GCC-GalaxyS3-GPU-Mali400-Arm7-Debug with some GL
errors:
http://build.chromium.org/p/client.skia.android/builders/Test-Android-GCC-Gal...

I have hard time reproing it with a local S3 Mali400, and hard time
understanding why the patch would affect the device.. Still, maybe revert is in
order..

[Kimmo Kinnunen, 2015-07-31 12:55:51]

On 2015/07/31 12:53:40, Kimmo Kinnunen wrote:
> So this fails Test-Android-GCC-GalaxyS3-GPU-Mali400-Arm7-Debug with some GL
> errors:
>
http://build.chromium.org/p/client.skia.android/builders/Test-Android-GCC-Gal...
> 
> I have hard time reproing it with a local S3 Mali400, and hard time
> understanding why the patch would affect the device.. Still, maybe revert is
in
> order..

N/M: skbug.com/3947