"afaik Chromebooks are all ARM now"
This isn't correct. Chromebooks/ChromeOS are meant to be processor neutral just like Android.
The Samsung XE303C12 device released a few months ago is the only current official Chromebook device that is ARM based among half a dozen devices, most of which are x86, and Google hasn't said anything to suggest that they are shifting Chromebooks to the ARM exclusively.
In fact, the latest Chromebook release (Acer's C7, which was released after the Samsung ARM one) is an x86 device.