gtkwindow: bail out on WM operations in the presence of grabs
gtkwindow: bail out on WM operations in the presence of grabs

These operations will require a grab on the WM side, so we can spare the
attempt from the WM to take a grab when we're certain it won't suceed.

https://bugzilla.gnome.org/show_bug.cgi?id=752327

davidgumberg/gtk,jadahl/gtk,alexlarsson/gtk,alexlarsson/gtk,jigpu/gtk,jadahl/gtk,jadahl/gtk,jadahl/gtk,alexlarsson/gtk,jigpu/gtk,grubersjoe/adwaita,jigpu/gtk,davidgumberg/gtk,davidgumberg/gtk,chergert/gtk,grubersjoe/adwaita,chergert/gtk,chergert/gtk,alexlarsson/gtk,jigpu/gtk,davidgumberg/gtk,grubersjoe/adwaita,grubersjoe/adwaita,davidgumberg/gtk,grubersjoe/adwaita,jigpu/gtk,chergert/gtk,jadahl/gtk,chergert/gtk,jadahl/gtk,chergert/gtk,jigpu/gtk,alexlarsson/gtk,alexlarsson/gtk,jadahl/gtk,jigpu/gtk,chergert/gtk,chergert/gtk,jigpu/gtk,davidgumberg/gtk,grubersjoe/adwaita,alexlarsson/gtk,davidgumberg/gtk,jadahl/gtk,davidgumberg/gtk,alexlarsson/gtk,grubersjoe/adwaita,grubersjoe/adwaita