Disable window move by dragging of the blank area of the tab bar correctly after https://bugzilla.mozilla.org/show_bug.cgi?id=1241275
Disable window move by dragging of the blank area of the tab bar correctly after https://bugzilla.mozilla.org/show_bug.cgi?id=1241275

See alsp #16

piroor/tabsonbottom,piroor/tabsonbottom