commit 6b9ab853 changed the
behavior of the class, but the header comments were not updated.
This commit adds comments for the new behavior.

Also: The tested behavior in the unittest was changed.
This commit adapts the unittest name to the new behavior.

Change-Id: Ia364ebbc3e2bfe1b0b8e3e26269a3c162e1a05d1
Reviewed-on: https://gerrit.libreoffice.org/17510Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>