Fix GrCoverageSetOpXP unit test on mixed samples

Fix GrCoverageSetOpXP unit test on mixed samples

Updates GrCoverageSetOpXPFactory::TestCreate to not invert coverage
with mixed samples, which is an unsupported configuration.

TBR=bsalomon@google.com

BUG=skia:4556
Committed: https://skia.googlesource.com/skia/+/c94cd7cc01b655b7f4289537962c36a4ee8dd63e

[Chris Dalton, 2015-11-12 19:44:43]

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

[egdaniel, 2015-11-12 19:54:27]

lgtm

[Chris Dalton, 2015-11-12 19:54:47]

The CQ bit was checked by cdalton@nvidia.com

[commit-bot: I haz the power, 2015-11-12 19:54:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1442763002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1442763002/1

[commit-bot: I haz the power, 2015-11-12 19:56:02]

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

[commit-bot: I haz the power, 2015-11-12 19:56:02]

Try jobs failed on following builders:
  skia_presubmit-Trybot on client.skia.fyi (JOB_FAILED,
http://build.chromium.org/p/client.skia.fyi/builders/skia_presubmit-Trybot/bu...)

[egdaniel, 2015-11-12 20:10:10]

Description was changed from

==========
Fix GrCoverageSetOpXP unit test on mixed samples

Updates GrCoverageSetOpXPFactory::TestCreate to not invert coverage
with mixed samples, which is an unsupported configuration.

BUG=skia:4556
==========

to

==========
Fix GrCoverageSetOpXP unit test on mixed samples

Updates GrCoverageSetOpXPFactory::TestCreate to not invert coverage
with mixed samples, which is an unsupported configuration.

TBR=bsalomon@google.com

BUG=skia:4556
==========

[egdaniel, 2015-11-12 20:10:17]

The CQ bit was checked by egdaniel@google.com

[commit-bot: I haz the power, 2015-11-12 20:10:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1442763002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1442763002/1

[commit-bot: I haz the power, 2015-11-12 20:11:07]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/c94cd7cc01b655b7f4289537962c36a4ee8dd63e

[bsalomon, 2015-11-12 21:08:28]

otherwise lgtm

https://codereview.chromium.org/1442763002/diff/1/src/gpu/effects/GrCoverageS...
File src/gpu/effects/GrCoverageSetOpXP.cpp (right):

https://codereview.chromium.org/1442763002/diff/1/src/gpu/effects/GrCoverageS...
src/gpu/effects/GrCoverageSetOpXP.cpp:250: bool invertCoverage =
!d->fRenderTarget->hasMixedSamples() && d->fRandom->nextBool();
Can you add a comment here about why?