Remove transitional GN code.

Remove transitional GN code.

The conditionals were added to facilitate a two-sided build GN config update
where the default optimization config was renamed. This is complete so the
transitional code can be removed.

Committed: https://crrev.com/7ec3be731fa53fe50af88dd59829fccb34836c0f
Cr-Commit-Position: refs/heads/master@{#30733}

[brettw, 2015-09-14 23:02:36]

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

[brettw, 2015-09-14 23:02:36]

Feel free to press the CQ button. Thanks!

[jochen (gone - plz use gerrit), 2015-09-15 07:36:46]

The CQ bit was checked by jochen@chromium.org

[jochen (gone - plz use gerrit), 2015-09-15 07:36:47]

lgtm

[commit-bot: I haz the power, 2015-09-15 07:36:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1338163003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1338163003/20001

[commit-bot: I haz the power, 2015-09-15 08:43:32]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-09-15 08:43:43]

Patchset 2 (id:??) landed as
https://crrev.com/7ec3be731fa53fe50af88dd59829fccb34836c0f
Cr-Commit-Position: refs/heads/master@{#30733}