I would point you towards this: https://kver.wordpress.com/2015/09/18/on-ad-blocking-trackin... Unfortunately development is at a standstill right now. More hands on deck are needed. If other people will not participate at first it might not even use CEF as planned. Using CEF would be great because it will eventually allow it to use both Servo and Blink.

Also worth mentioning is the other (than Vivaldi) let's recreate classic Opera project: http://otter-browser.org/

Of course both of these are very very young projects and aren't really ready to replace Firefox.