Maybe you're not responsible, but if someone says "something changed in the OS and your previous method is now adding substantial overhead", you could either a)

Maybe you're not responsible, but if someone says "something changed in the OS and your previous method is now adding substantial overhead", you could either a) report the change to the OS and mitigate or b) report the change to the OS and ignore the problem for years. It sounds like Mozilla chose b, for whatever reason. As a software developer, I've had to workaround many many bugs in OSs, especially when dealing with updates to Android. It's just part of the job.