There is no static, universal default password for the chronos account on an updated machine.
sudo passwd -d chronos
is the default local username for the Linux shell (command line) when your Chromebook is in Developer Mode . It is not your Google account password. chronos password chromebook
If you have just entered Developer Mode and accessed the Chrome Shell (Crosh) or a TTY (Ctrl+Alt+F2 or Ctrl+Alt+F3), you will encounter a login prompt. There is no static, universal default password for