This is a follow up to the conversation at https://gerrit.wikimedia.org/r/#/c/323337/4/includes/models/MobileCollection.php.
Basically, MF PHP codebase has a use case where it would be more efficient to check for emptiness of a collection rather than counting its elements and comparing it to 0.
- Create a new interface with one method only, e.g. isEmpty, to check for emptiness of a collection object.
- The interface should live in MF for now and then be upstreamed to core if need be.
- Audit the MF codebase and replace the use of count( $object ) === 0 with $collectionInstance->isEmpty() where needed.