Definitely a very handy feature "Unlock your screen with just a simple PIN" touch devices is soon for heading to Chrome OS powered notebooks.
This experimental feature available in the latest Dev channel update is currently in test mode. The functionality is disable by default but can be easily enabled through the Chrome flag—so, you all you have to do is simply enable the flag chrome://flags/#quick-unlock-pin.
Then restart Chrome, and head over to Chrome Material Design settings page to set up your Lock Screen PIN in the new "Screen Lock" section.
When it's done, lock your screen with ?? + L and enjoy the new unlock experience!
Additionally, the team also notes, that they're very soon planning on moving the "Quick unlock" settings in the regular Chrome settings page in an upcoming update.
The 'Quick unlock' feature is being touted as a very useful feature for touch screen devices as they won't have to tap in long and cumbersome passwords each time they want to unlock their device.
There's no information just yet on when it will happen, but it's very likely whenever the current Dev channel moves to the Stable channel.