"Notification ranker" - what does it do, and what happens if I disable it?
From arstechnica:


  GoogleExtServices has an app name of "Android Services Library" and
  does actually contain something: an "Android Notification Ranking
  Service." A "Notification Ranking Service" was added in Lollipop, and
  it sorts notifications by "importance" based on things like freshness,
  app type (IM apps come first), and by contact. This seems to be an
  extension to the system that includes support for Nougat's
  "notification bundling" feature. This is a really minor feature, and
  with only this single chunk of code, GoogleExtServices weighs in at a
  microscopic 10KB.