Set stage outline layer to top

Outline do not set layer before so it will show behind tasks layer
then it will be invisible. Set its layer to top to ensure it's
visible.

Also fix context error message bug by replacing display context to
window context.

Fix: 192902371
Fix: 192527238
Test: Enable spilt and disable it many times and check outline display
Test: Check ContextImpl log
Change-Id: Ic1796965d7254d2276d4c05c662e940820c8d995