A protocol for registering a 'fuchsia.ui.views.Focuser' to be used by an accessibility service.
Accessibility services can drastically alter the way an user interacts with a system. For example, instead of changing the focus from one view to another using the touch screen, this user may use voice. For this reason, accessibility services need a way to be able to request focus to whatever view on the system, as this request can come in any form of input, not necessarily the one that normally drives focus in a particular device.
The request from the accessibility service assumes that whoever implements this protocol associates this request with a view that sits high in the view hierarchy.