am 17af14d8: Merge change 2289 into donut

Merge commit '17af14d8133f99b5e886d830e92e38ba1da7cc2d'

* commit '17af14d8133f99b5e886d830e92e38ba1da7cc2d':
  Add AIDL files for the TTS service and the associated callback service (to signal synthesis completion).