Add GL_TRANSFORM_FEEDBACK_BUFFER_MODE to GetProgramiv query.

Add GL_TRANSFORM_FEEDBACK_BUFFER_MODE to GetProgramiv query.

It's simply an overlook in previous CLs.

BUG=429053
TEST=gpu_unittests, webgl2_conformance
R=piman@chromium.org

Committed: https://crrev.com/6e2bb1f1a489c4b3cae0ea8e7f819ae93c3f54c6
Cr-Commit-Position: refs/heads/master@{#348759}

[Zhenyao Mo, 2015-09-14 20:56:09]

The CQ bit was checked by zmo@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-09-14 20:56:54]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1341133002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1341133002/20001

[Zhenyao Mo, 2015-09-14 20:56:56]

zmo@chromium.org changed reviewers:
+ kbr@chromium.org

[Zhenyao Mo, 2015-09-14 20:56:57]

piman, kbr: PTAL

I discovered this bug by running one of the WebGL2 conformance tests. With this
CL, that test case passes.

[piman, 2015-09-14 22:11:25]

lgtm

[commit-bot: I haz the power, 2015-09-14 23:06:01]

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

[commit-bot: I haz the power, 2015-09-14 23:06:01]

Dry run: This issue passed the CQ dry run.

[Zhenyao Mo, 2015-09-14 23:06:14]

The CQ bit was checked by zmo@chromium.org

[commit-bot: I haz the power, 2015-09-14 23:08:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1341133002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1341133002/20001

[commit-bot: I haz the power, 2015-09-14 23:19:02]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-09-14 23:19:44]

Patchset 2 (id:??) landed as
https://crrev.com/6e2bb1f1a489c4b3cae0ea8e7f819ae93c3f54c6
Cr-Commit-Position: refs/heads/master@{#348759}

[Ken Russell (switch to Gerrit), 2015-09-15 01:02:40]

Excellent. LGTM after the fact.

[commit-bot: I haz the power, 2015-09-23 12:38:49]

Patchset 2 (id:??) landed as
https://crrev.com/6e2bb1f1a489c4b3cae0ea8e7f819ae93c3f54c6
Cr-Commit-Position: refs/heads/master@{#348759}