Clipchamp, now a Microsoft product, isn't supported in Firefox. From the WebCompat bug, where one of their engineers commented, we've learned that there are a couple of platform features and bugs that are relevant here.
Let's use this metabug to keep track of those!
Tentatively adding bug 1486454 as another dependency, as per the comment in the web-bug. It might be a different performance issue, but it's worth keeping track of that in some way.