Follow-up for  Ife38c2cd94ac9902911b005dbbca8b0d0a62e6d7

Address review comments on the previous CL.
(Plus a couple bug fixes.)

Test: atest BatterySaverPolicyTest
Test: manual test
Bug: 68769804
Change-Id: If2de9148d1b8175a9f0d66bc3a7ecd02ce7a620b
5 files changed