Make TrafficStats uid attribution @SystemApi

Anything that runs as a singleton may need to attribute traffic to
various client apps; in particular, backup transports need to do this.
Apropos of which, introduce a @SystemApi method specifically for that
purpose, setThreadStatsTagBackup().

Bug 16661321

Change-Id: Id5d22e28bdc68edb53f2a1fdba80b144fcbc61d2
1 file changed
tree: 97681b1f0156b686e1b60487391da792ee31d2be
  1. core/
  2. services/
  3. wifi/