We have stopped pushing the affected version of Keystone, so if your computer has not been broken yet, it won't be.

If it has been broken but not rebooted:

  sudo rm -rf /Library/Google/GoogleSoftwareUpdate/GoogleSoftwareUpdate.bundle
  sudo ln /private/var /var

should fix it. That deletes Keystone and fixes the symlink. If it has been rebooted, these commands at a recovery console should repair the computer.

Chrome will subsequently ask for admin credentials to reinstall the updater next time you run it. This will not re-break the computer; the version of Keystone bundled with Chrome is older, and we have stopped serving the version affected by this issue.