Hi,
I use Firefox 40.0.3 from Fedora 21 updates repository
$ rpm -q firefox
firefox-40.0.3-1.fc21.x86_64
Every PKI CA certificate profile containing keyGenInputImpl input produces warning message on a web page:
Warning: This version of Firefox no longer supports the crypto web object used to generate and archive keys from the browser. As a result expect limited functionality in this area.
But actually key generation works in my Firefox version.