Merge changes I638ed5cd,I29f15571,I21a22ed1

* changes:
  Expose registerDefaultNetworkCallbackAsUid.
  Support calling registerDefaultNetworkCallback for another UID.
  Store the effective UID in NetworkRequestInfo.
tree: 963fe0d42f71ba15a2f0c1b58e06bbac29ac3a80
  1. framework/
  2. service/
  3. OWNERS
  4. TEST_MAPPING