These tests are for the Origin Isolation feature, and supplement those in external/wpt to specifically test Chromium origin trial mechanisms.
The abbreviation oiot means “first the Origin-Trial header, then the Origin-Isolation header”. Conversely, otoi means "first the Origin-Isolation header, then the Origin-Trial header.
The tokens for the Origin-Trial header are generated using the commands
python tools/origin_trials/generate_token.py https://web-platform.test:8444 OriginIsolationHeader --expire-timestamp=2000000000 python tools/origin_trials/generate_token.py https://www.web-platform.test:8444 OriginIsolationHeader --expire-timestamp=2000000000