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
When we enter the overview, we don't explicitly don't take a grab, so we
shouldn't connect to key-focus-changed and things like that, otherwise
random overview code will drop our grab for us.
This fixes escape in the overview not dropping when a notification is up.
Make sure to account for modalCount properly, rather than just
tracking modalCount for the last actor on the stack. Additionally,
traverse the popped actors in the reverse order so that onUngrabbed
callbacks are called at the proper place in time.
