code: function commit_tunnel() {
              tunnel.onstatechange = chained_tunnel.onstatechange;
              tunnel.oninstruction = chained_tunnel.oninstruction;
              tunnel.onerror = chained_tunnel.onerror;
              chained_tunnel.uuid = tunnel.uuid;
              committedTunnel = tunnel;
          }
docs: Use the current tunnel from this point forward. Do not try any more
  tunnels, even if the current tunnel fails.
  
  @private