If the user has the mouse down - for example when they are selecting
text and dragging - then the attempt to get a modal grab will fail.
grabHelper: allow the .grab() function to fail and do nothing in this
modal case if the grab fails.
messageTray: handle grab failure and don't pop up the tray. Change the
logic for tray dwelling so that we only try to pop up the tray once
while the pointer is in the dwell area - this avoids the possiility
that the tray will pop up once the user releases the mouse.
https://bugzilla.gnome.org/show_bug.cgi?id=682385
3902e8bff0