Fatal errors that should trigger the fallback UI and halt execution by throwing an exception.
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);
}