Revert of Remove OneClickSigninHelper since it is no longer used.

Revert of Remove OneClickSigninHelper since it is no longer used. (patchset #5 id:340001 of https://codereview.chromium.org/914363003/)

Reason for revert:
Broke the tab_switching.tough_energy_cases benchmark on the perf bots.

BUG=465692
Original issue's description:
> Remove OneClickSigninHelper since it is no longer used.
>
> BUG=260022, 350202
>
> Committed: https://crrev.com/be592667bdf919fb8292c88c1b59767add856ba4
> Cr-Commit-Position: refs/heads/master@{#319662}

TBR=noms@chromium.org,asvitkine@chromium.org,sky@chromium.org,rogerta@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=260022, 350202
Committed: https://crrev.com/861ae783973af63043c05ebe3ba250cc36c45c3d
Cr-Commit-Position: refs/heads/master@{#319862}

[rmcilroy, 2015-03-10 11:59:51]

Created Revert of Remove OneClickSigninHelper since it is no longer used.

[commit-bot: I haz the power, 2015-03-10 12:00:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/998513002/1

[commit-bot: I haz the power, 2015-03-10 12:00:49]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-10 12:01:39]

Patchset 1 (id:??) landed as
https://crrev.com/861ae783973af63043c05ebe3ba250cc36c45c3d
Cr-Commit-Position: refs/heads/master@{#319862}