Continue refactoring of MediaFocusControl

Move RemoteControlClient death handler and remote playback state
 inside MediaController class.
Make MediaController data fields private. Document which accessors
 can be removed once the audio focus and media button receiver
 mechanisms are dissociated.

Change-Id: Icd14fb0d99bf74512c8f8552d124c0353ce1f06d
2 files changed