Enable gbm platform by default in ozone builds

Enable gbm platform by default in ozone builds

Now that we have minigbm in third_party we can set ozone_platform_gbm=1 by default.

BUG=530712
TEST=tryjobs for linux_chromium_chromeos_ozone_rel_ng,
  cast_shell_linux

Committed: https://crrev.com/88e504e383e7641e139bc836b33ded00a0d46668
Cr-Commit-Position: refs/heads/master@{#348802}

[spang, 2015-09-14 23:19:05]

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

[commit-bot: I haz the power, 2015-09-14 23:20:57]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1336023002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1336023002/20001

[spang, 2015-09-14 23:25:39]

spang@chromium.org changed reviewers:
+ dpranke@chromium.org

[Dirk Pranke, 2015-09-14 23:43:18]

lgtm

[commit-bot: I haz the power, 2015-09-14 23:56:53]

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

[commit-bot: I haz the power, 2015-09-14 23:56:54]

Dry run: Try jobs failed on following builders:
  cast_shell_linux on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)

[spang, 2015-09-15 00:13:33]

The CQ bit was checked by spang@chromium.org

[commit-bot: I haz the power, 2015-09-15 00:14:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1336023002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1336023002/20001

[commit-bot: I haz the power, 2015-09-15 01:21:35]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-09-15 01:22:53]

Patchset 2 (id:??) landed as
https://crrev.com/88e504e383e7641e139bc836b33ded00a0d46668
Cr-Commit-Position: refs/heads/master@{#348802}

[spang, 2015-09-15 23:46:24]

A revert of this CL (patchset #2 id:20001) has been created in
https://codereview.chromium.org/1342323002/ by spang@chromium.org.

The reason for reverting is: Broke chrome-sdk builds until it updates.
.

[commit-bot: I haz the power, 2015-09-23 12:40:50]

Patchset 2 (id:??) landed as
https://crrev.com/88e504e383e7641e139bc836b33ded00a0d46668
Cr-Commit-Position: refs/heads/master@{#348802}