No translation key used in autosave.js

var autosaveLabel = new Element('label',

Unknown macro: {'class'}

);
autosaveLabel.appendChild(this.autosaveCheckbox);
autosaveLabel.appendChild(document.createTextNode(" Autosave"));
var frequencyLabel = new Element('label',

Unknown macro: {'class'}

);
frequencyLabel.appendChild(document.createTextNode("every "));
frequencyLabel.appendChild(this.autosaveInput);
this.timeUnit = new Element('span');
this.setTimeUnit();
frequencyLabel.appendChild(document.createTextNode(" "));
frequencyLabel.appendChild(this.timeUnit);

Confirmed by Vincent Massol here:
https://forum.xwiki.org/t/are-these-strings-translatable-or-not/3895/9