Fix dm with Chromium command buffer driver

Fix dm with Chromium command buffer driver

Fix a crash in dm when run with Chromium command buffer driver.

Also removes glCopyTextureCHROMIUM, it does not seem to be used.
This is removed on the grounds that it would need similar change,
if it was used. The variable fCopyTextureCHROMIUM does not seem to
be populated in the Chromium side, either.

BUG=skia:2992
Committed: https://skia.googlesource.com/skia/+/0adfffba1bee55eee9e31e809cd0089840722b26

[Kimmo Kinnunen, 2015-10-12 07:04:37]

kkinnunen@nvidia.com changed reviewers:
+ bsalomon@google.com, hendrikw@chromium.org

[hendrikw, 2015-10-12 18:12:53]

On 2015/10/12 07:04:37, Kimmo Kinnunen wrote:

This crash happening last week, looks like it was introduced by
https://codereview.chromium.org/1376293003

LGTM.  Can you update the bug to "skia:2992"?  Thanks!

[Kimmo Kinnunen, 2015-10-13 03:28:11]

The CQ bit was checked by kkinnunen@nvidia.com

[commit-bot: I haz the power, 2015-10-13 03:28:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1389213004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1389213004/20001

[commit-bot: I haz the power, 2015-10-13 03:28:22]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from valid reviewer(s) till 2015-10-13 09:28 UTC

[commit-bot: I haz the power, 2015-10-13 03:29:31]

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

[commit-bot: I haz the power, 2015-10-13 03:29:32]

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...)

[bsalomon, 2015-10-13 18:01:19]

On 2015/10/13 03:29:32, commit-bot: I haz the power wrote:
> 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...)

Lgtm

[hendrikw, 2015-10-13 19:57:42]

The CQ bit was checked by hendrikw@chromium.org

[commit-bot: I haz the power, 2015-10-13 19:57:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1389213004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1389213004/20001

[commit-bot: I haz the power, 2015-10-13 19:58:41]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/0adfffba1bee55eee9e31e809cd0089840722b26