Bug#862441: [mutter] backport fix for at-spi reporting the wrong position of gnome-shell elements

[intrigeri]

Control: tag -1 + moreinfo

anonym:
> Versions before mutter 3.24 are affected by a bug making gnome-shell report the wrong x-coordinate of its elements via at-spi. For details, see: 

It would be nice to sum up the impact of the bug here (e.g. for users
of universal access technologies), so the maintainers and the release
team don't have to go through additional hops to understand why this
normal severity bug should be fixed in Stretch.

Thanks in advance!