See discussion in bug 313496

Testcase in URL field shows that we can get the same effect with a min-width style rule...

Same thing with listboxes: data:text/html,<select size=10></select><select size=10 style="min-width:2.5em"><option style="display:none"></select>

Summary of changes: 1) Remove dummy select stuff completely 2) Change the code that calculates a height for something like <select size="10"> to use the <select>'s font if there are no usable options. This makes select heights happy. 3) Make the code that draws the focus outline do the same thing to determine the height of the focus rect when there are no child frames. 4) Add a rule to forms.css that sets a width on empty selects. I decided that this was better than setting a min-width, since doing it this way plays nice with author style sheets setting all three of width, min-width, max-width. This setup is not dynamic on option removal/addition (unlike what we used to have) because the :empty selector is not dynamic, but that's something I think we should fix by fixing :empty.

Fixed on trunk.