Intermittent failure in /css/css-fonts/generic-family-keywords-002.html #40929

  ▶ OK /css/css-fonts/generic-family-keywords-002.html
  │   ▶ PASS [expected FAIL] font-family: -webkit-generic(fangsong) treated as <font-family>, not <generic-name>
  │   │ PASS [expected FAIL] font-family: -webkit-generic(kai) treated as <font-family>, not <generic-name>
  │   │ PASS [expected FAIL] font-family: -webkit-generic(khmer-mul) treated as <font-family>, not <generic-name>
  │   └ PASS [expected FAIL] font-family: -webkit-generic(nastaliq) treated as <font-family>, not <generic-name>
  │   ▶ FAIL [expected PASS] font-family: -webkit-serif treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-sans-serif treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-cursive treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-fantasy treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-monospace treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-system-ui treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-math treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-ui-serif treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-ui-sans-serif treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-ui-monospace treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-ui-rounded treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: NonGenericFontFamilyName treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-body treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-standard treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: -webkit-pictograph treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: emoji treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: fangsong treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ FAIL [expected PASS] font-family: BlinkMacSystemFont treated as <font-family>, not <generic-name>
  │   │   → assert_equals: expected 30 but got 50
  │   │ 
  │   │ runTests/</<@http://web-platform.test:8000/css/css-fonts/generic-family-keywords-002.html:37:20
  │   │ Test.prototype.step@http://web-platform.test:8000/resources/testharness.js:2869:25
  │   │ test@http://web-platform.test:8000/resources/testharness.js:633:30
  │   │ runTests/<@http://web-platform.test:8000/css/css-fonts/generic-family-keywords-002.html:36:11
  └   └ runTests@http://web-platform.test:8000/css/css-fonts/generic-family-keywords-002.html:35:14