Fix dm failures after Cleanup legacy NVPR-related definitions

Fix dm failures after Cleanup legacy NVPR-related definitions

Non-NV_path_rendering drivers should always return NULL context
for NVPR context type request. Fix this.

This was needed due to the previous patch trying to implement below:
NV_path_rendering drivers should return non-NULL context
for NVPR context type request, regardless whether path
rendering is actually supported or not. This is due to SAN
bots having older drivers and trying to run nvprmsaa config.

Committed: https://skia.googlesource.com/skia/+/8b2b3807e6c0dac956666f26f87e1a660e4921b8

[Kimmo Kinnunen, 2015-07-01 10:47:51]

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

[Kimmo Kinnunen, 2015-07-01 10:47:52]

Broke the bots again.. :(

[Kimmo Kinnunen, 2015-07-01 11:18:36]

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

[borenet, 2015-07-01 11:24:28]

LGTM

[borenet, 2015-07-01 11:24:36]

The CQ bit was checked by borenet@google.com

[commit-bot: I haz the power, 2015-07-01 11:24:43]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1220513005/1

[commit-bot: I haz the power, 2015-07-01 11:24:44]

The author kkinnunen@nvidia.com has not signed Google Contributor License
Agreement. Please visit https://cla.developers.google.com to sign and manage
CLA.

[commit-bot: I haz the power, 2015-07-01 11:31:07]

The author kkinnunen@nvidia.com has not signed Google Contributor License
Agreement. Please visit https://cla.developers.google.com to sign and manage
CLA.

[commit-bot: I haz the power, 2015-07-01 11:31:32]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/8b2b3807e6c0dac956666f26f87e1a660e4921b8