Checked with 7/6 master build Test run such as |./mach web-platform-tests _mozilla/service-workers/service-worker/resource-timing.https.html| Result: * Harness status: OK * Found 2 tests * 2 Fail: ** Controlled resource loads *** assert_unreached: unexpected rejection: entry is undefined Reached unreachable code unreached_rejection/<@https://web-platform.test:8443/_mozilla/service-workers/service-worker/resources/test-helpers.sub.js:42:7 Test.prototype.step@https://web-platform.test:8443/resources/testharness.js:1363:20 Test.prototype.step_func/<@https://web-platform.test:8443/resources/testharness.js:1387:1 Promise*@https://web-platform.test:8443/_mozilla/service-workers/service-worker/resource-timing.https.html:29:5 Test.prototype.step@https://web-platform.test:8443/resources/testharness.js:1363:20 async_test@https://web-platform.test:8443/resources/testharness.js:513:13 @https://web-platform.test:8443/_mozilla/service-workers/service-worker/resource-timing.https.html:24:1 ** Non-controlled resource loads *** entry is undefined @https://web-platform.test:8443/_mozilla/service-workers/service-worker/resource-timing.https.html:55:5 Test.prototype.step@https://web-platform.test:8443/resources/testharness.js:1363:20 test@https://web-platform.test:8443/resources/testharness.js:496:9 @https://web-platform.test:8443/_mozilla/service-workers/service-worker/resource-timing.https.html:52:1 * Traces: https://pastebin.mozilla.org/8838624

Does not seem like something we should support in v1