Push_js.notification_action
method action : Js_of_ocaml.Js.js_string Js_of_ocaml.Js.t Js_of_ocaml.Js.prop
method title : Js_of_ocaml.Js.js_string Js_of_ocaml.Js.t Js_of_ocaml.Js.prop
method icon : Js_of_ocaml.Js.js_string Js_of_ocaml.Js.t Js_of_ocaml.Js.prop