am 9077f8ec: Merge "Not all audio source has the drift time information" into gingerbread

Merge commit '9077f8ec931a4c080948a85ce2e0f793f65e9b62' into gingerbread-plus-aosp

* commit '9077f8ec931a4c080948a85ce2e0f793f65e9b62':
  Not all audio source has the drift time information