Ask when power button is pressed should allow PC shutdown without using keyboard/mouse

When "When power button is pressed" is set to "Ask", pressing the power button shows dialog allowing to choose the action. However we cannot shutdown PC without using keyboard or mouse and it's hard to shutdown without connected screen. Sometimes there's need to properly shutdown PC without peripherals connected.

Suggestion is adding a configurable timeout for shutdown action. Press a power button and display dialog, but after e.g. 20 seconds it'll automatically shutdown when user doesn't select any option or cancel the dialog.