UPower_policyQuality of service policy
type latency_request = {lr_uid : int;The user ID that issued the request.
*)lr_pid : int;The process ID of the application.
*)lr_exec : string;The executable that issued the request.
*)lr_timespec : int64;The number of seconds since the epoch.
*)lr_persistent : bool;If the request is persistent and outlives the connection lifetime.
*)lr_typ : latency;The type of the request.
*)lr_reserved : string;lr_value : int;The value, in microseconds or kilobits per second.
*)}val get_latency_requests : UPower.t -> latency_request list Lwt.tval requests_changed : UPower.t -> unit OBus_signal.tval latency_changed : UPower.t -> (latency * int) OBus_signal.t