It isn't shared in any way; the object is created anew each time.
ReferencedMemoryStream itself uses a shared_prt internally, for
referencing the data.
Change-Id: I78bf63af2e4476c55680bf33843e9ccd47b1080d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/191725
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>