The design is very simply expressed :
An offer is needed for a request if and only if that offer
might beat the satisfier for that request.
The implementation of "might beat" is NetworkRanker#mightBeat.
Test: FrameworksNetTests FrameworksWifiTests NetworkStackTests
Bug: 167544279
Change-Id: I0fe911eef2483ecbac48c733d56283b81538690a