Mark final fields as such.
Group mutex protected fields together with the mutex that protects them.
Always access mutex protected fields under the mutex.
Bug: 28798823
Change-Id: I96cdd5e063babb73e9f124107c5576c47801f34b
Test: Compiles, Wifi tethering continues to work on angler.
(cherry picked from commit 7b30e548a5)