Make mixed samples contingent on auxiliary extensions

Make mixed samples contingent on auxiliary extensions

Moves the cap for mixed samples into GrShaderCaps and does not enable
it unless we have support for both dual source blending and
multisample disable.

Creates a dedicated cap for multisample disable.

Reconfigures the mixed samples cap to indicate the collective
capability of three different extensions:

  GL_NV_framebuffer_mixed_samples
  GL_NV_sample_mask_override_coverage
  GL_EXT_raster_multisample

Imports tokens and procedures for GL_EXT_raster_multisample.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/0edea2c8e76a9f5340a7a4960193757c4a5fb227

[Chris Dalton, 2015-05-21 03:28:52]

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

[Chris Dalton, 2015-05-21 03:28:52]

https://codereview.chromium.org/1151793002/diff/1/src/gpu/gl/GrGLCaps.cpp
File src/gpu/gl/GrGLCaps.cpp (right):

https://codereview.chromium.org/1151793002/diff/1/src/gpu/gl/GrGLCaps.cpp#new...
src/gpu/gl/GrGLCaps.cpp:258: fMultisampleDisableSupport = false;
This will eventually be replaced with a check for the ES extension.

[bsalomon, 2015-05-21 14:27:29]

lgtm

BTW we are thinking seriously about never disabling multisampling and making the
contract be that all draws and clips on a multisampled target are always
antialiased regardless of the paint setting.

[Chris Dalton, 2015-05-21 14:45:48]

On 2015/05/21 14:27:29, bsalomon wrote:
> lgtm
> 
> BTW we are thinking seriously about never disabling multisampling and making
the
> contract be that all draws and clips on a multisampled target are always
> antialiased regardless of the paint setting.

Ok, that shouldn't be a problem. There are certain scenarios with mixed samples
where we will still want to disable it, but those are unrelated to the places
where the code currently disables multisample.

In that case would you rather have this done without a dedicated
multisampleDisable cap? I don't care much either way...

[bsalomon, 2015-05-21 15:09:20]

On 2015/05/21 14:45:48, Chris Dalton wrote:
> On 2015/05/21 14:27:29, bsalomon wrote:
> > lgtm
> > 
> > BTW we are thinking seriously about never disabling multisampling and making
> the
> > contract be that all draws and clips on a multisampled target are always
> > antialiased regardless of the paint setting.
> 
> Ok, that shouldn't be a problem. There are certain scenarios with mixed
samples
> where we will still want to disable it, but those are unrelated to the places
> where the code currently disables multisample.
> 
> In that case would you rather have this done without a dedicated
> multisampleDisable cap? I don't care much either way...

It's fine to keep it as is for now.

[Chris Dalton, 2015-05-21 15:16:01]

The CQ bit was checked by cdalton@nvidia.com

[commit-bot: I haz the power, 2015-05-21 15:16:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1151793002/1

[commit-bot: I haz the power, 2015-05-21 15:27:49]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/0edea2c8e76a9f5340a7a4960193757c4a5fb227