This patch simplifies CallbackHandler in the following way:
- CallbackHandler directly uses the static references to
sNetworkCallback and sCallbackRefCount. This allows to remove
instance fields in CallbackHandler.
- CallbackHandler does not have a reference to ConnectivityManager
anymore
- CallbackHandler.getObject() is now generic in a type-safe way.
Test: ConnectivityServiceTest passes
Bug: 28537383
Bug: 32130437
Change-Id: I5004da5b91498e6ff7f8b05057a9e24b975bb56e
d42650faaa