ash::AppListPresenterDelegate listens to device entering/exiting Touch View mode via OnMaximizeModeStarted/OnMaximizeModeEnded callbacks and dismisses the app list if it is shown. We need a similar behavior implemented in Mustash.

There's are existing Mojo interfaces for touchview: https://cs.chromium.org/chromium/src/ash/public/interfaces/touch_view.mojom?q=touchview+mojo&sq=package:chromium&dr=C

Using them should work. Example usage in SigninScreenHandler: https://cs.chromium.org/chromium/src/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc?sq=package:chromium&dr=CSs&rcl=1481199532&l=302