Properly handle disabling sync via the google dashboard.

Properly handle disabling sync via the google dashboard.

Add SigninManager::ProhibitSignout() that the policy code can use to disable
signout. This makes our previous ad-hoc signout prohibition more stable by
catching other places where we might sign out (such as cancelling sync during
re-auth).

Add SigninManager::IsSignoutProhibited() which UI code that wants to show/hide
signout UI can call.

Restores old behavior where stopping sync via the google dashboard will try to
sign out the user.

Fixed sync UI to properly display the "Sync is stopped via the google dashboard"
message when sync is stopped on desktop platforms.

Updated sync settings code to trigger a re-auth flow when the user clicks on "Advanced Sync Setup..." when sync is stopped via the dashboard.

BUG=174134
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=182705

[Andrew T Wilson (Slow), 2013-02-14 18:15:54]

Roger, PTAL at browser/signin, browser/sync, and sync_setup_handler.cc

Dan, PTAL at browser_options_handler.cc

Joao, PTAL at browser/policy.

[Dan Beam, 2013-02-14 21:47:54]

browser_options_handler.cc lgtm

[Roger Tawa OOO till Jul 10th, 2013-02-14 21:58:34]

lgtm for browser/signin, browser/sync, and sync_setup_handler.cc

Once sign out is disabled by policy, we are guaranteed that
ProhibitSignoutIfNeeded() will always be called for that profile?

I ask because when you restart chrome for example, the prohibit flag is set to
false.  If sign out is prohibited then someone always needs to explicitly
prohibit it each time SM is created.

[Joao da Silva, 2013-02-15 06:38:22]

lgtm

[Andrew T Wilson (Slow), 2013-02-15 09:36:02]

On 2013/02/14 21:58:34, Roger Tawa wrote:
> lgtm for browser/signin, browser/sync, and sync_setup_handler.cc
> 
> Once sign out is disabled by policy, we are guaranteed that
> ProhibitSignoutIfNeeded() will always be called for that profile?
> 
> I ask because when you restart chrome for example, the prohibit flag is set to
> false.  If sign out is prohibited then someone always needs to explicitly
> prohibit it each time SM is created.

Yes, during profile init we load policy and set the flag.

[commit-bot: I haz the power, 2013-02-15 09:36:52]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/atwilson@chromium.org/12258036/2001