It seems to me that a large volume of code in Blink deals with obscure features with relatively niche use cases (such as WebRTC, WebUSB,WebGL, WebAudio and so on and so forth), which would mean a large amount of programmer effort for very little user-facing gain.
Additionally, in these areas, web standards tend to say 'whatever Chrome does', with FF often lifting large parts of Chrome code to support these features. Even if the above wasn't true, in practicality it is, since all clients are tested against Chrome, you'd need to follow all its quirks to have your browser be compatible.
Are you planning to do a clean room implementation of these features as well?
