Clean up old field trial activation code.

Clean up old field trial activation code.

None of these are needed anymore since trials
can be marked as "starts_active" server-side.

BUG=none

Committed: https://crrev.com/b860144c20ad3b3f7ecabacf8f39c9e7924d8e29
Cr-Commit-Position: refs/heads/master@{#293237}

[Alexei Svitkine (slow), 2014-09-03 17:43:32]

asvitkine@chromium.org changed reviewers:
+ jwd@chromium.org

[jwd, 2014-09-03 19:29:56]

LGTM
nit: activition -> activation in cl description.

[Alexei Svitkine (slow), 2014-09-03 21:10:56]

The CQ bit was checked by asvitkine@chromium.org

[commit-bot: I haz the power, 2014-09-03 21:21:23]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/asvitkine@chromium.org/536033002/1

[commit-bot: I haz the power, 2014-09-04 00:32:11]

Committed patchset #1 (id:1) as 388a143800f22d36c66c9eb97efa5880f6bfc504

[commit-bot: I haz the power, 2014-09-10 03:29:04]

Patchset 1 (id:??) landed as
https://crrev.com/b860144c20ad3b3f7ecabacf8f39c9e7924d8e29
Cr-Commit-Position: refs/heads/master@{#293237}