We have a scene which can easily get 30/60 fps in chrome depending on resolution. With firefox its dropping as low as 12.
Using the firefox profiler, it looks like the issue is in the animations:
requestAnimationFrame is currently taking around 80-85ms
During periods of fps up jump,
requestAnimationFrame seems to drop to around 70ms so it looks like there is a strong correlation.
Looking at the Frame steps duration
It appears there is a large chunk of time unaccounted for.
When I tried to dig deeper, there seems to a lot of time waiting around in Gecko if I am reading it right