Merge "Offer an ApkSignerEngine implementation." am: 6975f03fd8 am: 2c7da1d5c7
am: 7b9641d153

* commit '7b9641d1538ff127ad0e65669101f2c52f232cb1':
  Offer an ApkSignerEngine implementation.

Change-Id: I91b6d42e294cf5f2413a5769ec17e31538bff685