Add experiment for enabling frames and screenshots

[sbuggay]

Summary

Allow RNDT to append frames and screenshots, if the trace contains those events.

Test plan

Tested locally against an RN build that emits these events.

• This change maintains backwards compatibility with previous Local Storage data (if modifying settings, experiments, or other persisted client state).

Upstreaming plan

Removes fork.

• This commit should be sent as a patch to the upstream devtools-frontend repo following the contribution guide for Meta employees OR contribution guide.
• This commit is React Native-specific and cannot be upstreamed.

[hoxyq]

Since this was a fork, we don't need to upstream this, I've updated the summary.

In terms of sequencing this work, it should probably be like this:

1. Land support for frames in RN.
2. Update the fork so that Frames track is appended, but screenshots checkbox is still hidden.
3. Sync the frontend.
4. Land support for screenshots in RN.
5. Remove the fork completely.
6. Sync the frontend.

I think your current change will just append the track, but the checkbox will still be hidden, right? So you implemented step [2] here?

Also, could you please remove the isReactNative field from the class, I believe it is unused now?

[sbuggay]

@hoxyq
Removed references to isReactNative.
Agreed on sequencing. Yes this change is only step 2 and has no affect on the screenshots checkbox.

[hoxyq]

Awesome!

I think we would also need to add support for parsing enabled categories in Tracing.start method, which would be the source of truth if user requested capturing screenshots or not.

[huntie]

Thanks!