You can even contribute to them without a Firefox clone, they're an entirely separate repo that contains a webpage that can be run in both Firefox or Chrome as a regular website and used to debug both. It's fun!
Debugger.html repo: https://github.com/devtools-html/debugger.html
Example of a network timeline.
I get a better representation of the timeline waterfall in Chrome.
Like I said, the tools are almost there.