Add a helper for managing remote playback.

The RemotePlaybackClient class helps take care of identifying
remote playback capabilities, formatting requests, parsing results,
and managing sessions.  The goal is to remove confusion around the
usage of the protocol by providing a more familiar API surface
to work with.

Bug: 10260186
Change-Id: I49a6dcfa30ff8b7a57655a39a43317ebb3add2a0
2 files changed