expose some sync control methods
- ActiveSyncInfo
- ContentResolver.addStatusChangeListener
  - SYNC_OBSERVER_TYPE_SETTINGS
  - SYNC_OBSERVER_TYPE_PENDING
  - SYNC_OBSERVER_TYPE_ACTIVE
- make the ContentService resilient to nulls passed in to the
  status change listener registration and unregistration calls

bug http://b/issue?id=2337197
6 files changed