GLX_EXT_tetxure_from_pixmap operates on a GLXPixmap, which takes a
reference on the backing pixmap; that GLXPixmap might be long-lived, so
we should account for it in ResQueryClientPixmapBytes.
Acked-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Adam Jackson <ajax@redhat.com>