Use Google Play Services' analytic-specific library (6.5+)

[jonalmeida]

Play Services will be splitting up their massive library into smaller sets. When this comes out we should update to use only the analytics part that contains the Advertising ID.

Granular Dependency Management
As we’ve continued to add more APIs across the wide range of Google services, it can be hard to maintain a lean app, particularly if you're only using a portion of the available APIs. Now with Google Play services 6.5, you’ll be able to depend only on a minimal common library and the exact APIs your app needs. This makes it very lightweight to get started with Google Play services.

See: http://android-developers.blogspot.ca/2014/11/google-play-services-65.html

[alexanderdean]

Good thinking!