WifiService: add build properties abstraction

As it turns out, WifiStateMachine isn't the only thing that
wants to change its logging behavior depending on
Build.TYPE.

1) Add an abstraction of Build.TYPE, so that we can
   a) check build type in a common way, and
   b) test the logging behavior across build types
2) Migrate WifiStateMachine to use this new abstraction.

BUG=28822027
TEST=unit tests

Change-Id: I6f4cb00ccb5f3a4b9a5b67e69f8365aab7fd429c
5 files changed
tree: a9daf81554a95fae9ffc1b25e027f429c8ee7353
  1. service/
  2. tests/