Hostility?

I think that Google is far more interested in the capability existing then in writing/controlling it themselves.

They started Chrome because Firefox wasn't doing a good job, the competition has caused Firefox to shape up significantly

they started Chrome OS because nobody else was working on an OS that would fit a similar niche, If Canonical does a good job with something like this, I don't see any reason for Google to try to crush it, I think it would be more likely that Google would instead try to support it. Google gets almost the same the benefit without having to do all the engineering, and more importantly, the support work.