This allows the session to turn off all of its UI. Use it in onCreate() to prevent the session from ever creating any of its UI. Switched the window creation and initialization to happen lazily to support this. Test: New test added to android.assist.cts.LifecycleTest Bug: 30999386 Change-Id: I8eacb3697c8ac9908c50b9577abea2d20597b016