With this, it's possible to tell which view shell created which undo
actions. It's visible only in the doc model xml dump only, though.
Change-Id: Ia76d218a1d8b578aaad00ab733c772b10dda39f0
Reviewed-on: https://gerrit.libreoffice.org/27693
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>