<!doctype html> <input type=text> <script> let input = SpecialPowers.wrap(document.querySelector("input")); SpecialPowers.Cc["@mozilla.org/satchel/form-fill-controller;1"].getService(SpecialPowers.Ci.nsIFormFillController).markAsAutofillField(input); input.getBoundingClientRect(); // previewValue setter depends on the reframe posted by markAsAutofillField() having being processed... input.previewValue = "Autofill"; SpecialPowers.wrap(window).windowUtils.addManuallyManagedState(input, "autofill"); </script>