Before that depsgraph tagging was done from inside notifier listener in
viewport. This had the following issues:
- If there are no viewports, selection tag was not done. Causing possible
issues when object becomes visible.
- Required special trickery to detect which data to tag for update.
- Was causing crash when transforming/selecting markers in clip editor.
This is because selecting marker needed to poke viewport to redraw, since
selected bundles will be displayed differently in viewport.
