Fix all issues with SystemUI visibility and transitions

- Use win.isVisible again to determine top opaque full screen
window. !goneForLayout isn't really correct as windows that are
just about to draw can already influence SystemUI flags
- Don't coalesce messages in CommandQueue. This messes up ordering!
Bad!

Test: Unlock to Settings
Test: Navigate around in settings, make sure no flashes
Test: Cold launch United app
Test: Go to recents <-> settings 10 times

Change-Id: I15d37b35344d955c45591386182c5266bba74f01
Fixes: 37926053
Fixes: 37433095
Fixes: 37923474