Firefox and isSelected issue

Trying to make a gform_pre_render manipulate a dropdown field and mark one as selected, it was not working... Until I swapped to Chrome and it was ok.

Seems that this FF behavior is not new. It displays the last selected field after refreshing.
http://stackoverflow.com/q/4831848/1287812

I'm solving like this:

add_filter( 'wp_head', 'gf_is_selected_firefox' );

function gf_is_selected_firefox()
{
	if( !preg_match( '/Firefox/i', $_SERVER['HTTP_USER_AGENT'] ) )
		return;
	?>
	<script>
		window.onload = function() { document.forms['gform_5'].reset(); };
	</script>
	<?php
}

PS.: here, no detection is being made to only print this in the correct page where the form is being displayed.