I'm a Firefox user working at Google. A lot of internal tools are Chrome only and when they get released to public they have a lot of technical debt to make it compatible with FF. The thing is engineer seems to always go for the latest internal library like Polymer which are only supported by Chrome. FF is working on supporting it which would probably improve the situation for a lot of Google product but it's taking time.

Also I've heard that Google is not so good at hiring front end engineer, as they are less likely to have the "inverse a binary tree" background.