given that we are largely caching SalBitmap here, and none of the subclasses want to do anything more sophisticated, we can do the implementation in the base class. Change-Id: I5211933e9a431c8ff46625ef30666c89106ce7ad Reviewed-on: https://gerrit.libreoffice.org/c/core/+/184529 Tested-by: Jenkins Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>