Screenshots are dropped, if you untick "Include hidden threads" when uploading

[dholbert]

STR:

1. Capture a profile, using the Gecko Platform configuration.
2. Verify that you can see a screenshots track in the profile that you just captured.
3. Click "upload" at the top right of your profile.
4. On the upload doorhanger-dialog, untick "Include Hidden Threads" (but be sure to leave "Include screenshots" checked)
5. Click the Upload button on the dialog
6. Look for screenshots in the resulting web-hosted profile.

ACTUAL RESULTS: The screenshots track is gone; screenshots seem to have been excluded in the uploaded profile.

EXPECTED RESULTS: Screenshots should've been included, since I had the "Include Screenshots" checkbox checked.

Sample profile created with the STR (which is lacking screenshots as a result of this bug): https://share.firefox.dev/3ciYB4q

┆Issue is synchronized with this Jira Task

[julienw]

Thanks for filing this bug! Indeed this is a problem we have. We thought of the other way around (remove the screenshots when keeping the track) but not of the other way.

See https://github.com/firefox-devtools/profiler/issues/3149#issuecomment-768961764 for an explanation and a possible solution. I believe we could fix the 2 bugs with 1 patch.

Note: I think we have the logic to move screenshot markers to another thread, because we do that for the comparison functionality.