Chrome OS devices that are on the Dev channel have received a new update in the last few days which enables device unlocking with a simple PIN. The functionality is disabled by default but can be easily enabled through the Chrome flags menu and then by heading over to the Chrome Material Design settings page to set up the feature.
Google is planning on moving the 'Quick unlock' setting over to the regular Chrome settings page soon in an upcoming update, according to François Beaufort who announced the availability of the feature. There's no information just yet on how long it will take to appear on the Stable channel, but will likely be whenever the version in the Dev channel matures to the Stable channel in the following months.
In his post to Google+, Beaufort wrote:
“This experimental feature is currently being tested in the latest Dev update. All you have to do is enable the flag chrome://flags/#quick-unlock-pin, restart Chrome, and go to Chrome Material Design settings page for now to set up your Lock Screen PIN in the new "Screen Lock" section. When it's done, lock your screen with [Search] + L and enjoy the new unlock experience!”
The 'Quick unlock' feature is being touted as useful for users with touch screen devices as they won't have to tap in long and cumbersome passwords each time they want to unlock their device.