Modern webkit needs to be linked to a modern version of chromium, otherwise it doesn't compile. If you try to use an old version and a new webkit, you're gonna get a lot of errors. If you try to use a modern version of the javascript engine in an old version of Chromium, you're gonna get errors. If you are gonna try to use the new UI with the old version, you're gonna get errors. Besides, Google doesn't care about old webkits and doesn't archive them nor support them, so it would even be impossible to compile an old version unless you do save it, store it, and use it. Let's suppose that you start back from version 49 and you modify it with newer components. The first obstacle you're gonna face is going to be the sandbox, which is not compatible with XP. Simply put, I have no idea what they did with that browser, but if they are willing to share the code and make contributions, they're welcomed.
If you wanna contribute yourself, though, you're more than welcome and you can do it here: https://github.com/Skulltrail192/Chromium-For-XP-SRV2003
I wouldn't trust anything made by Chinese companies, by the way, as they showed what they were capable of with Maxthon... (sending visited websites, bookmarks, computer informations and a list of running processes back to Beijing).