[Android] Enable root in perf_control.SetHighPerfMode.

[Android] Enable root in perf_control.SetHighPerfMode.

SetHighPerfMode needs root, but it currently only checks to see if
we already have root rather than trying to enable it.

BUG=478104
Committed: https://crrev.com/83c5ba866887f876d3cd45473a839d60b5036166
Cr-Commit-Position: refs/heads/master@{#329980}

[jbudorick, 2015-05-14 22:44:26]

jbudorick@chromium.org changed reviewers:
+ sullivan@chromium.org

[sullivan, 2015-05-14 22:46:06]

lgtm

Thanks for the quick fix!

[jbudorick, 2015-05-14 22:46:57]

The CQ bit was checked by jbudorick@chromium.org

[commit-bot: I haz the power, 2015-05-14 22:49:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1135393005/1

[commit-bot: I haz the power, 2015-05-15 00:00:36]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-15 00:01:29]

Patchset 1 (id:??) landed as
https://crrev.com/83c5ba866887f876d3cd45473a839d60b5036166
Cr-Commit-Position: refs/heads/master@{#329980}