For some explanation see http://blog.roumanoff.com/2015/09/using-webcrypto-api-to-generate-keypair.html
There is no way to generate a ssh keypair on a chromebook, but we have access to chrome and the webcrypto API. I had to do all sorts of gymnastics to convert the generated keypair to something that can be consummed by SSH.
The end result is a usable single page app that will locally generate a keypair you can save to local drive. Allowing you to do that straight from chrome on a chrome book.
Everywhere else, you should have access to ssh-keygen which is the recommended way to generate keypair for SSH.