async start() {
    const positionUpdates = await this.getPositionUpdates();
    positionUpdates.forEach((positionUpdate) => {
      this.createMarker_(positionUpdate);
    });
    if (this.getBroadcastPositionUpdates) {
      this.getBroadcastPositionUpdates(this.updateMarkerPositions_.bind(this));
    } else {
      this.pollServer_();
    }
    if (this.getUserDisconnects) {
      this.getUserDisconnects(this.disposeMarker_.bind(this));
    }
  }
Initialize the workspace by creating and registering markers for all active
users and activating the handling of recieving PositionUpdates from the server.
@public