Please describe the problem:
i have few screenshots to make my bug clearer.

when tab in epiphany is moved, it's moved instantly, but with black background on tab, as seen on transparent pixels in tab.

pidgin, terminal, gedit and epiphany - all of these aren't using same way to move them, but they're still using same gui library - gtk.

Steps to reproduce:
1. open minimum 1 additional if tabbar is shown only for 1 < tabs in you config.
2. move tab.


Actual results:
black pixels are shown

Expected results:
i see black pixels

Does this happen every time?
yes

Other information:
it's gtk-theme independent