Intermittent failure in /css21_dev/html4/pseudo-elements-001.htm

[Manishearth]

http://build.servo.org/builders/linux-rel-css/builds/24

  ▶ Unexpected subtest result in /css21_dev/html4/pseudo-elements-001.htm:
  │ FAIL [expected PASS] transition padding-left on :before, changing content / values
  │   → assert_not_equals: may not be target value while transitioning on .pseudo got disallowed value "10px"
  │ FAIL [expected PASS] transition padding-left on :after, changing content / values
  │   → assert_not_equals: may not be target value while transitioning on .pseudo got disallowed value "10px"
  │ 
  │ root.generalParallelTest.assertIntermediateValuesFunc/<@http://web-platform.test:8000/css21_dev/html4/support/generalParallelTest.js:223:17
  │ Test.prototype.step@http://web-platform.test:8000/resources/testharness.js:1227:20
  │ .cases.values.done@http://web-platform.test:8000/css21_dev/html4/pseudo-elements-001.htm:94:29
  │ runLoop/</</</<@http://web-platform.test:8000/css21_dev/html4/support/runParallelAsyncHarness.js:122:26
  │ Test.prototype.step@http://web-platform.test:8000/resources/testharness.js:1227:20
  │ runLoop/</</<@http://web-platform.test:8000/css21_dev/html4/support/runParallelAsyncHarness.js:121:21
  │ runLoop/</<@http://web-platform.test:8000/css21_dev/html4/support/runParallelAsyncHarness.js:120:17
  └ runLoop/<@http://web-platform.test:8000/css21_dev/html4/support/runParallelAsyncHarness.js:118:13

[bholley]

Disabling this test in #14300 for too many intermittent failures with signoff from @Manishearth.