Add a global setting for "Auto sign-in".

Add a global setting for "Auto sign-in".

The setting is used for Credential Manager API.

BUG=400674
Committed: https://crrev.com/cbcd16e93cc1a1a0c8cf0d68077336144766c5bb
Cr-Commit-Position: refs/heads/master@{#314118}

[vasilii, 2015-01-30 16:41:49]

vasilii@chromium.org changed reviewers:
+ mkwst@chromium.org

[vasilii, 2015-01-30 16:42:08]

Hi Mike,

please review the CL.

[Mike West, 2015-01-31 09:53:09]

Hrm. Putting the pref in the component means that bringing it into the setting
UI would be a layering violation, doesn't it?

[Mike West, 2015-02-02 08:31:57]

On 2015/01/31 09:53:09, Mike West wrote:
> Hrm. Putting the pref in the component means that bringing it into the setting
> UI would be a layering violation, doesn't it?

I talked to vabr@ this morning, and he explained to me that components can
indeed be references from Chrome's settings UI. I find this a bit strange, as
Blink's modules have exactly the opposite dependency structure, but whatever. :)

LGTM.

[vasilii, 2015-02-02 09:20:23]

The CQ bit was checked by vasilii@chromium.org

[commit-bot: I haz the power, 2015-02-02 09:21:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/890943002/1

[commit-bot: I haz the power, 2015-02-02 09:24:46]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-02 09:25:47]

Patchset 1 (id:??) landed as
https://crrev.com/cbcd16e93cc1a1a0c8cf0d68077336144766c5bb
Cr-Commit-Position: refs/heads/master@{#314118}