Add new GM that exercises Gray 8 mipmapping and sRGB-ness

Add new GM that exercises Gray 8 mipmapping and sRGB-ness

This demonstrates the bug that was fixed by:
  https://codereview.chromium.org/2088883002/

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2087933002

Committed: https://skia.googlesource.com/skia/+/79b15f60f4e5893cf93d20e3f0bd6ae6560e1351

[Brian Osman, 2016-06-21 20:11:17]

Description was changed from

==========
Add new GM that exercises Gray 8 mipmapping and sRGB-ness

This demonstrates the bug that was fixed by:
  https://codereview.chromium.org/2088883002/

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

to

==========
Add new GM that exercises Gray 8 mipmapping and sRGB-ness

This demonstrates the bug that was fixed by:
  https://codereview.chromium.org/2088883002/

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2087933002
==========

[Brian Osman, 2016-06-21 20:11:43]

The CQ bit was checked by brianosman@google.com to run a CQ dry run

[commit-bot: I haz the power, 2016-06-21 20:11:56]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2087933002/1

[Brian Osman, 2016-06-21 20:11:57]

brianosman@google.com changed reviewers:
+ bsalomon@google.com

[commit-bot: I haz the power, 2016-06-21 20:30:27]

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

[commit-bot: I haz the power, 2016-06-21 20:30:28]

Dry run: This issue passed the CQ dry run.

[bsalomon, 2016-06-21 20:38:08]

lgtm

[Brian Osman, 2016-06-21 20:39:08]

The CQ bit was checked by brianosman@google.com

[commit-bot: I haz the power, 2016-06-21 20:39:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2087933002/1

[commit-bot: I haz the power, 2016-06-21 20:40:15]

Description was changed from

==========
Add new GM that exercises Gray 8 mipmapping and sRGB-ness

This demonstrates the bug that was fixed by:
  https://codereview.chromium.org/2088883002/

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2087933002
==========

to

==========
Add new GM that exercises Gray 8 mipmapping and sRGB-ness

This demonstrates the bug that was fixed by:
  https://codereview.chromium.org/2088883002/

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2087933002

Committed:
https://skia.googlesource.com/skia/+/79b15f60f4e5893cf93d20e3f0bd6ae6560e1351
==========

[commit-bot: I haz the power, 2016-06-21 20:40:16]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/79b15f60f4e5893cf93d20e3f0bd6ae6560e1351