Revert of 🌅 Refactor SigninHelper.

Revert of 🌅 Refactor SigninHelper. (patchset #3 id:40001 of https://codereview.chromium.org/1860143003/ )

Reason for revert:
Some static methods in SigninHelper are used when Chrome is not started, so native is not loaded. See crbug.com/605832 for context.

Original issue's description:
> Refactor SigninHelper.
>
> Rather than expose static methods and passing in the context of the
> caller, since SigninHelper is designed to be used application-wide,
> save the application context as a member variable instead.
>
> Save the default shared preferences as a member variable, reducing
> potential burden in the future.
>
> BUG=600806, 599284
>
> Committed: https://crrev.com/53511f941065102f8c8c5a476c5e4cc3770726ee
> Cr-Commit-Position: refs/heads/master@{#387905}

TBR=maxbogue@chromium.org,nyquist@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=600806, 599284
Committed: https://crrev.com/1d491ec4d5956c60fbf72e8cb5d3b27c842f9e6b
Cr-Commit-Position: refs/heads/master@{#390091}

[Peter Wen, 2016-04-27 15:06:21]

Created Revert of 🌅 Refactor SigninHelper.

[commit-bot: I haz the power, 2016-04-27 15:06:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1926703003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1926703003/1

[commit-bot: I haz the power, 2016-04-27 15:31:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1926703003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1926703003/1

[commit-bot: I haz the power, 2016-04-27 16:01:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1926703003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1926703003/1

[commit-bot: I haz the power, 2016-04-27 16:09:35]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-04-30 17:10:17]

Patchset 1 (id:??) landed as
https://crrev.com/1d491ec4d5956c60fbf72e8cb5d3b27c842f9e6b
Cr-Commit-Position: refs/heads/master@{#390091}

[commit-bot: I haz the power, 2016-04-30 17:50:14]

Description was changed from

==========
Revert of 🌅 Refactor SigninHelper. (patchset #3 id:40001 of
https://codereview.chromium.org/1860143003/ )

Reason for revert:
Some static methods in SigninHelper are used when Chrome is not started, so
native is not loaded. See crbug.com/605832 for context.

Original issue's description:
> Refactor SigninHelper.
> 
> Rather than expose static methods and passing in the context of the
> caller, since SigninHelper is designed to be used application-wide,
> save the application context as a member variable instead.
> 
> Save the default shared preferences as a member variable, reducing
> potential burden in the future.
> 
> BUG=600806,599284
> 
> Committed: https://crrev.com/53511f941065102f8c8c5a476c5e4cc3770726ee
> Cr-Commit-Position: refs/heads/master@{#387905}

TBR=maxbogue@chromium.org,nyquist@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=600806,599284
==========

to

==========
Revert of 🌅 Refactor SigninHelper. (patchset #3 id:40001 of
https://codereview.chromium.org/1860143003/ )

Reason for revert:
Some static methods in SigninHelper are used when Chrome is not started, so
native is not loaded. See crbug.com/605832 for context.

Original issue's description:
> Refactor SigninHelper.
>
> Rather than expose static methods and passing in the context of the
> caller, since SigninHelper is designed to be used application-wide,
> save the application context as a member variable instead.
>
> Save the default shared preferences as a member variable, reducing
> potential burden in the future.
>
> BUG=600806,599284
>
> Committed: https://crrev.com/53511f941065102f8c8c5a476c5e4cc3770726ee
> Cr-Commit-Position: refs/heads/master@{#387905}

TBR=maxbogue@chromium.org,nyquist@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=600806,599284

Committed: https://crrev.com/1d491ec4d5956c60fbf72e8cb5d3b27c842f9e6b
Cr-Commit-Position: refs/heads/master@{#390091}
==========