STR:

1. open the popup
2. click Java
3. close the popup
4. open the popup again

=> Java isn't selected

This does it because we filter out unsupported features, but only at load time in the popup or when using the shortcut keys. This means we don't do it when we start the profiler after checking an unsupported feature, or from the devtools panel (including in remote debugging). This pretty much indicates that this filtering is quite useless at the moment, as the profiler will likely just ignore any unknown feature.

Instead we should put the suported features to our state at load time (including fetching them from the actor for the remote debugging use case) so that we can filter the checkbox in the settings panel itself.

This is where the filtering currently happens: https://searchfox.org/mozilla-central/rev/088e2cf29c59d733d57af43903eb0267dbf72e2a/devtools/client/performance-new/popup/background.jsm.js#332

What's even more misleading is that at step 4, when Java isn't selected, it's still part of the stored preference but won't be used when starting the profiler using the popup or the keys, but will be used when using the devtools panel. It will be removed only if the user selects other features.

I think this will be resolved by Bug 1585659, which I'm actively working on.

Fixed by Bug 1585659.