The latest build of the Chrome OS Canary Channel was updated with support for fingerprint scanners. Version 58.0.3007.0 introduces the feature as an experimental flag that can be enabled by visiting "chrome://flags" on your Chromebook. After that's said and done, opening the Screen Lock menu of your Settings app will allow you to set up the new functionality provided you're already signed into the device. The latest Chrome Dev build supports up to five fingerprints and this feature was apparently included in the update that rolled out last week, as reported by Chrome Story.
The code refers to this feature as the Quick Unlock and currently only allows users to dismiss their lock screens once they've already signed into their Chromebooks. Naturally, there's currently no easy way to test this new functionality seeing how a Chromebook boasting an integrated fingerprint scanner has yet to hit the market. On the other hand, the code suggests that this feature should work just fine with an external fingerprint scanner that connects to a Chromebook, so you may be able to try out Quick Unlock if you have access to one of those devices. Support for fingerprint scanners isn't the only unlock method of the Chrome OS that's currently in testing as a recent Chrome Dev update also introduced the option to unlock a Chromebook with a PIN.
As for Chromebooks featuring fingerprint scanners, evidence pointing to such devices has been circulating the industry for almost half a year now, but we're yet to see them hit the market. Recent rumors suggest that the first Chrome OS computer with an integrated fingerprint scanner is codenamed "Eve," and previous reports suggested that a laptop referred to as "Kevin" will also ship with a fingerprint sensor. The fact that support for those devices is now a part of an experimental Chrome OS build certainly suggests that Chromebooks equipped with fingerprint readers will launch sooner rather than later, possibly by spring. Once that happens, Chromebooks will finally support a functionality that was already offered by laptops running Windows and macOS for some time now. More information on the matter will hopefully follow in the coming weeks.