Offline Maps on New Google Maps for iOS (v2) and Android (v7)

To download an area on the map, type 

ok maps

in the search box.

To clear the cached map, go to

Settings -> About, terms & privacy -> Terms & privacy 

and select

Clear application data

Refs
http://www.idownloadblog.com/2013/07/17/offline-maps-in-google-maps-2/