One of them is a board that's referred to as "cheza", and another commit that follows this reveals that "cheza" is the board overlay used on a Snapdragon 845 reference device. Some of the internal listings confirmed Google's plans. Meanwhile, the existing ARM-powered Samsung Chromebook Plus is also referenced in the comments.
This would be the first Qualcomm Snapdragon-powered Chromebook to hit the market, following speculation (which originated from Google employees) that Qualcomm wouldn't be involved in the Chromebook market due to its reluctance to deliver long-term Chromebook support.
The rk3399 is a mobile processor that's considerably less powerful than Qualcomm's Snapdragon 845, but it's also one of the few ARM-based chipsets that's powering a Chrome OS Chromebook.
Goodness knows when this might become reality, but the fact that it's being worked on is exciting enough! The "chipset-qc845" name is clearly a hint that the Qualcomm Snapdragon 845 is being used. However, Google has never fully embraced Qualcomm ARM processors for Chromebooks. It's not certain what has changed since Google made those claims last year but, if such code is going into Chrome OS now, Qualcomm may have made the necessary changes to make that happen.
One of the major reasons why Google is reluctant to use Qualcomm's chipsets is because it was only capable of providing two years of driver support. Earlier this month, Microsoft showed off Always Connected laptops from Asus and HP that were powered by Snapdragon 835 SoC. These laptops promise standby time of more than a week, support for 4G LTE and instant wake and sleep among other things.
Spotted in the Chromium repository (via XDA-Developers) are various references to "chipset-qc845", with the generic board for that chip codenamed "cheza".