Opera's multiple upload is shown in wrong z-order

It's about feature: F30-1840878
http://sourceforge.net/tracker/index.php?func=detail&aid=1840878&group_id=152762&atid=785194

In general, the content of uploaders should be shown in a content panel which use scroll bar to limit panel's size.

But in Opera, the content is overflowed and covers the components which are below it.