base

Fix 5863053: Add method to lock screen immediately.

This fixes a bug where the device fails to lock when DevicePolicyManagerService
requests the device to be locked and the screen was off because the user hit
the power button.

The change allows DPMS to directly invoke screen lock, bypasssing the screen state.

Change-Id: Iecdda6fc61e9c519119de495be23c69c3b983921