Angularjs - ng-map - Google Maps Javascript API v3 - how to Set best Zoom for Multiple markers

I'm using ngMap in an angularjs app. Iam displaying google-map with multiple markers onclick of Open map! button and first address present in the addresses array im taking as map center.

Here is The Plunk

All address related markers are displaying fine.

But how to set best zoom automatically for array of addresses, here these addresses i'm fetching from database, so these addresses changes for each request based on some condition.