Comment 16 for bug 826441

So I need to add here, changing the approach, or adding the user-stylesheet-uri support can still be done. In part I wanted to accelerate development by having existing API that extensions can already use. And I'd like adblock to do so as well. This way we can actually measure performance for instance.
- I fixed the issue with changing the font family, a notify was missing.
- Addons is applying the stylesheet now, the code was for some reason doing the opposite.