Comment 3 for bug 1193658

I'm not 100% sure how this feature works, but once the tab is outside the tabbar it's not asking to be drawn as a tab. I believe that at this point it's a window and no longer a tab. I imagine the solution would be to set the gtkstyle class (in the tabbar widget) to ".dynamic-notebook .notebook tab" for this window, but I have no idea if that would actually work.