I have a Firefox window with multiple tabs.  If I drag a tab onto a blank space on the desktop, Firefox is supposed to create a new window with its contents being that tab, and at the same time remove that tab from the original window.  This works fine in Windows.  This is on an up-to-date Arch installation with Firefox 43 but it has been a problem for a long time.  It did work back on KDE4.

Reproducible: Always

Steps to Reproduce:
1. Try to drag a Firefox tab and hover it over an open spot on the KDE desktop.  A grabber hand appears over the tab, a mini-icon is made of the page being dragged, the cursor changes from a grabber hand to an arrow with a "+" sign over it once the cursor is over the desktop, and a square outline appears on the desktop where the icon will be dropped.  So far, so good.  
2. Release the mouse button to make the drop happen.

Actual Results:  
I hear activity on my disk but the square outline that was on my desktop fades away and the Firefox tab is not created in a new window on the desktop.  The tab remains in the original window.

Expected Results:  
The tab should have closed from the original window and reopened in a new window.

- Works fine in Windows
- Used to work in KDE4
- Drag and drop of Konsole tabs onto the desktop to a new window works fine.