Just because Chrome is a winning formulation, doesn't mean it is the only one. My armchair example is themes... both chrome and ff now look like alien invaders of corporate identity on my desktop. While that makes sense for Google, it hurts Mozilla's image with the community of hackers/tinkers that love Firefox for features just like that one; features that quietly say, "its your browser, you likely know best". Especially because themes worked reasonably well for so long(at least from the users perspective, I'm told the implementation was fragile).
Maybe its time to go all in on the hacker community and make Firefox, a "Linux first" browser. The PC market shrinking, no one is arguing that. Trying to squabble over pieces of an ever shrinking pie is not a recipe for success.
This is especially true for Mozilla. All its competition can simply forget about their browser products and still be profitable. A failed Firefox likely means Mozilla disappearing for the digital landscape.
I propose that the Linux/Hacker community is the logical conclusion of PC itself and, by proxy, the PC browser market. Long after everyone has gone tablet or whatever, the last hold out of the PC market will be the Linux diehards, why not cater to them from the get go? You are going to be catering to them when all is said and done.
As a tangent, a great starting "performance feature", which is what all this e10s stuff is getting at, would be vaapi support for hardware accelerated video on linux. You can't really call your browser fast when it chokes the CPU on any 4k video. The the only browser to currently support it on linux... sigh... chromium.