code: public PlaybackState getFurthestPlaybackState() {
          PlaybackState result = null;
          for (PlaybackState state : playbackStateMap.values()) {
              if (result == null || result.position < state.position) {
                  result = state;
              }
          }
          return result;
      }
docs: Look up the playback state that has reached furthest in the track. This is used to render the “played until”
  graphic below the preview.
  
  @return the playback state, if any, with the highest {@link PlaybackState#position} value