Topbar SD status: only update when there are changes.
Topbar SD status: only update when there are changes.

Reduce the frequency at which UI updates are performed
to just those where the status might have changed.
The DOM is only changed when there are differences the user
could see.

Charcoal-SE/metasmoke,Charcoal-SE/metasmoke,Charcoal-SE/metasmoke,Charcoal-SE/metasmoke