Implement new mode for status bar, allowing it to overlay
windows that use WM.LP.FLAG_FULLSCREEN, and introduce
transparency.
No gesture is implemented yet, for now the auto-hiding
status bar can be shown using a debugging intent.
android.intent.action.HIDEYBARS
The auto-hiding status bar hides 3 seconds after shown,
or 3 seconds after last user-interaction with the shade.
Change-Id: Ie4bd625b9cbcddea8f818154719c7a6075972f2a
32beb2c6b1