Skip gl surface init when headless; enable wm apptests.

Skip gl surface init when headless; enable wm apptests.

Skip native_viewport's init of gfx::GLSurface when headless.
Remove the unused --use-osmesa flag (--use-test-config suffices?).
Re-enable the window_manager_apptests again; fingers crossed.

BUG=480040
TEST=Bot passes window_manager_apptests.
R=sky@chromium.org
TBR=jochen@chromium.org

Committed: https://crrev.com/84ba30ab51ce83cd8e4e34fbf5af0301af2033e6
Cr-Commit-Position: refs/heads/master@{#327184}

[msw, 2015-04-27 22:57:47]

Hey Scott; please take a look; thanks!
(sorry for the churn here!)

[sky, 2015-04-27 23:46:32]

LGTM

[msw, 2015-04-27 23:47:27]

The CQ bit was checked by msw@chromium.org

[commit-bot: I haz the power, 2015-04-27 23:49:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1103413002/20001

[commit-bot: I haz the power, 2015-04-27 23:57:10]

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

[commit-bot: I haz the power, 2015-04-27 23:57:11]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[msw, 2015-04-27 23:59:35]

msw@chromium.org changed reviewers:
+ jochen@chromium.org

[msw, 2015-04-28 00:00:17]

TBR'ing jochen@chromium.org for components/OWNERS.
(sky is adding new OWNERS files as we speak!)

[msw, 2015-04-28 00:00:21]

The CQ bit was checked by msw@chromium.org

[commit-bot: I haz the power, 2015-04-28 00:02:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1103413002/20001

[commit-bot: I haz the power, 2015-04-28 00:06:41]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-04-28 00:07:46]

Patchset 2 (id:??) landed as
https://crrev.com/84ba30ab51ce83cd8e4e34fbf5af0301af2033e6
Cr-Commit-Position: refs/heads/master@{#327184}