I tried the following and it seems that works to any browser:
<input id="passfld" type="text" autocomplete="off" />
<script type="text/javascript">
$(function(){
var passElem = $("input#passfld");
passElem.focus(function() {
passElem.prop("type", "password");
});
});
</script>
This way is much more safer than using timeout techniques, because it guaranties that the input field will yield to password when the user focuses it.