Comment 5 for bug 1432750

Looking into this a bit more (on Ubuntu, where it's more noticeable), we could set the TransientFor property for PlaceholderWindow.PlaceInFloatingFrame(). The downside is that the window is then "always on top", so you'd have to move or minimize it to uncover the base window.
I think this probably doesn't need to be a release blocker for 1.7, though.