Selector: Fix test iframe submission for firefox
Selector: Fix test iframe submission for firefox

Ref jquery/sizzle@20fbadb0870bd30e0e66c68891f121c0450374c4
(Cherry-picked from efc4f8d7814a8c44bd5b4d924d237a04263e1a85)

diracdeltas/jquery,sancao2/jquery,sancao2/jquery,diracdeltas/jquery,diracdeltas/jquery,sancao2/jquery