Add javadoc to NetworkStats related classes.

Bug: n/a
Test: n/a
Change-Id: If7f4d68ea89adbcbc02c1e0a06a11f6330f5d8f3
4 files changed
tree: db81e367f85d636984b09a6d904d59e0c65e28de
  1. core/
  2. packages/
  3. services/