Switch from using a weak reference (css::uno::WeakReferenceHelper) to the abstract XAccessibleContext UNO interface to a weak reference (unotools::WeakReference) of the more concrete OAccessible class in UnoControl. This makes clear that the accessible is always an OAccessible subclass and allows dropping some UNO-querying for the wanted UNO interfaces. Change-Id: Ib1ea66c83da9bbf76891c492d84aa57c396f2f44 Reviewed-on: https://gerrit.libreoffice.org/c/core/+/210459 Tested-by: Jenkins Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>