Having consistent import order will reduce chance of merge
conflict between internal and external master
Test: rebuild
Change-Id: I0b1a170967ddcce7f388603fd521f6ed1eeba30b
When DataSaverPreference is shown repeatedly, memory leak happens
since DataSaverBackend.Listener is not removed on onDetached().
TEST: Repeat enter and exit "Data usage" for
several times and check if the count of activity
is not increasing.
Bug: 72581115
Change-Id: Ic4a72de049bb87f1e522fe46dd0fb4bb58ed65a5
