Remove transitional GN build variable.

Remove transitional GN build variable.

The using_new_optimization_config existed to allow a multi-sided V8 build
update that is now complete.

TBR=dpranke

Committed: https://crrev.com/ae96775ac803adcc2a1ce95064ea46a6b75b95bf
Cr-Commit-Position: refs/heads/master@{#349212}

[brettw, 2015-09-16 19:34:47]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2015-09-16 19:35:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1351623003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1351623003/1

[commit-bot: I haz the power, 2015-09-16 20:12:40]

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

[commit-bot: I haz the power, 2015-09-16 20:12:41]

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

[brettw, 2015-09-16 20:21:33]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2015-09-16 20:23:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1351623003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1351623003/1

[commit-bot: I haz the power, 2015-09-16 20:36:03]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-16 20:36:50]

Patchset 1 (id:??) landed as
https://crrev.com/ae96775ac803adcc2a1ce95064ea46a6b75b95bf
Cr-Commit-Position: refs/heads/master@{#349212}

[Dirk Pranke, 2015-09-16 20:38:36]

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

[Dirk Pranke, 2015-09-16 20:38:36]

lgtm

[commit-bot: I haz the power, 2015-09-23 13:00:13]

Patchset 1 (id:??) landed as
https://crrev.com/ae96775ac803adcc2a1ce95064ea46a6b75b95bf
Cr-Commit-Position: refs/heads/master@{#349212}