[plasma-shell] [Bug 328593] Dual screen has regressed in plasma-shell

[Martin Gräßlin]

> I would close it. I'm sure there are issues but I would say they are mostly
> in kwin now.
> 
> KWin is regressing on dual screen too.

Please give a try to https://git.reviewboard.kde.org/r/117614/

I'm unsure about whether I want to ship it, but we need to do something. 
QDesktopWidget has regressed which KWin relies on. So going xrandr directly 
would be better, but I need more people to test the code.