Update shelf visibility when display configuration changes.

Shelf is supposed to be hidden on secondary diaplay on lock and login
screens. To reporduce the bug external display needs to be set as primary
screen and then attached while on lock screen. In that case external
monitor is first added as secondary and later set as primary. Shelf
visibility was not updated for the new secondary disply after the primary
display was changed.

Similar bug was also present for login screen. To fix it removing the early
return from ShelfLayoutManager::UpdateVisibilityState was needed. The issue
that required early return is already fixed.

Bug: 824504
Change-Id: I2e3b8e9d6427e3496e72651ba4be1bab538fe25c
Reviewed-on: https://chromium-review.googlesource.com/1052488
Commit-Queue: Aga Wronska <agawronska@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559922}
4 files changed