code: function error(msg) {
    // If multiple arguments were passed, pass them all to the log function.
    if (arguments.length > 1) {
      var logArguments = ['Error:'];
      logArguments.push.apply(logArguments, arguments);
      console.log.apply(console, logArguments);
      // Join the arguments into a single string for the lines below.
      msg = [].join.call(arguments, ' ');
    } else {
      console.log('Error: ' + msg);
    }
    console.log(backtrace());
    UnsupportedManager.notify(UNSUPPORTED_FEATURES.unknown);
    throw new Error(msg);
  }
docs: Fatal errors that should trigger the fallback UI and halt execution by throwing an exception.