This test just makes sense if webkit was build with NO_LISTBOX_RENDERING enabled.

You should see in the following table three comboboxes and no listboxes.

At the right cell you see a description of what should be the state of the elements just after loading this page.

combobox in previos cell should have option '1' selected.
combobox in previos cell should have no selected option.
combobox in previos cell should have no selected option.
after pressing this button all the combo boxes should go back to the state discribed above.