This shows back and IME switcher when in app taskbar
and IME is visible.
This doesn't remove the system bar just yet (will
show overlap). Next CL will remove the system IME buttons
so only launcher IME buttons show.
Bug: 191612881
Test: Used IME in gesture + 3 button with taskbar.
Change-Id: If39382c4d01f26a9350f7460d9e769ca9b57828c
Organize existing properties as follows:
- TaskbarViewController contains properties affecting TaskbarView (though child icons are still supplied by TaskbarHotseatController)
- TaskbarDragLayerController contains properties related to TaskbarDragLayer itself
- Renamed NavbarButtonUiController to NavbarButtonsViewController, following the pattern of TaskbarViewController and TaskbarDragLayerController
- TaskbarControllers contains the different controllers to make it easier to construct, initialize, destroy, and pass them around
- Removed TaskbarIconController as its responsibilities were moved to more specific controllers
Test: compiles and runs, manually tested
Bug: 187353581
Change-Id: Idccd95d47117101bf9617e5532a5b87635d2b8f6