After testing with the patches from Bug 1904870, I'm at the same point as comment 4, meaning the patches fix the STRs but don't work with the mochitest being added in the patch from Alex. Will investigate.
Bug 1834799 Comment 6 Edit History
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After testing with the patches from Bug 1904870, I'm at the same point as comment 4, meaning the patches fix the STRs but don't work with the mochitest being added in the patch from Alex. Will investigate. Edit: Found it, it's just because we were not accepting the CORS URL in the observer in the test.