It's hard to tell from the pictures, but I think any form of welding is going to discolor the chrome plating. Could that depression be filled with an epoxy, like MarineTex and the tab that is broken off put back on top of the epoxy, effectively gluing it back on ? If you cleaned up the mating surfaces really good to get good "tooth" to the parts it would help the bonding process. I have repaired boat exhaust manifolds with MarineTex, and you can even drill and tap it, so I know it is strong. Just a suggestion. Don