Android Police have an article up mentioning that Google is reportedly working on getting Steam working officially and supported on Chrome OS. While the details of this are a little sketchy, since neither Valve or Google have announced this, Android Police claim they spoke directly to Kan Liu at CES, the Director of Product Management for Google's Chrome OS who told them of their plans to make it happen.
Note: You can get Steam working on it in some form with some manual effort now, although it's not great. This seems to be about making it all official. Having it properly integrated, enabling ease of use would be good, part of what Chrome OS is supposed to be about—being simple and easy.
Weird though, typical Google perhaps with plans that don't quite fit into what they're doing elsewhere. Since Google are pushing their own gaming service with Stadia, you wouldn't expect them to do this. Gaming is a massive and powerful market though, giving a big boost to Chrome OS and Chromebooks with advertising that it works with Steam could definitely make some waves.
Chromebooks have historically been quite low-powered devices, for the most part anyway. However, that has been changing and they're continuing to get beefier devices with more storage (which would be important for this) out across different manufacturers. With more powerful AMD-based Chromebooks apparently planned, it might actually make a little sense given they would actually be able to run some of the games on Steam for Linux.
Another reason why developers may want to ensure their games work on Linux to then gain Chrome OS compatibility too? Sure, sounds good. Let's not get ahead of ourselves though, this type of project could be a long time away if it ever happens. Who knows, could be one of the reasons or just a possible use case for Valve's Gamescope.