Merge 176755

Merge 176755
> [sync] [chromeos] Fix setup flow when sync data is cleared via dashboard and sync is set up again
> 
> On Chrome OS, when a user clears their sync data via the dashboard, logs
> out, logs in again, and attempts to set up sync once more, the setup
> flow ends up getting stuck after the backend is initialized, because
> SigninTracker does not respond to the OnStateChanged call from
> ProfileSyncService::OnBackendInitialized.
> 
> This regression can be traced back to r171190, where SigninTracker was
> no longer initialized with the SigninTracker::SERVICES_INITIALIZING
> state in SyncSetupHandler::DisplayConfigureSync. This was causing
> SigninTracker to drop the OnStateChanged call from ProfileSyncService
> in the scenario where the user attempted to set up sync while already
> signed in to the Chrome OS device after clearing sync data via the
> dashboard.
> 
> This patch restores the initial SigninTracker state in
> SyncSetupHandler::DisplayConfigureSync. It also fixes the
> unittests that were previously failing in the original CL.
> 
> BUG=167090, 168064, 168875, 81265
> TEST=On ChromeOS, clear the dashboard, log out, log in, and set up sync.
> 
> Review URL: https://codereview.chromium.org/11824021

TBR=rsimha@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=177806