I made a slight modification to Adam Roach's code that makes it work in Safari and Chrome for Mac. Just use his instructions and it should work.
Code:
javascript:window.open("data:text/html,<center><b>Enter%20new%20name:</b><form%20method='get'%20action='https://www.aa.com/reservation/renameReservationSubmitAjax.do'><input%20name='reservationName'><input%20type='submit'%20value='Change'></form></center>","rename","width=400,height=40");