Intermittent PASS/FAIL in /css/cssom-view/scroll-behavior-smooth-navigation.html

[delan]

https://github.com/servo/servo/actions/runs/4571674861 (#29534)

  ▶ OK /css/cssom-view/scroll-behavior-smooth-navigation.html
  │   ▶ FAIL [expected PASS] /css/cssom-view/scroll-behavior-smooth-navigation.html
  │   │   → assert_equals: Shouldn't be scrolled back to top yet. expected 0 but got 18631
  │   │ 
  │   │ instant/window.onhashchange/window.onhashchange/<@http://web-platform.test:8000/css/cssom-view/scroll-behavior-smooth-navigation.html:48:24
  │   │ Test.prototype.step@http://web-platform.test:8000/resources/testharness.js:2595:25
  │   └ instant/window.onhashchange/window.onhashchange@http://web-platform.test:8000/css/cssom-view/scroll-behavior-smooth-navigation.html:46:38
  │   ▶ FAIL [expected PASS] /css/cssom-view/scroll-behavior-smooth-navigation.html
  │   │   → assert_not_equals: Shouldn't be scrolled to top anymore. got disallowed value 0
  │   │ 
  │   │ smooth/window.onhashchange/<@http://web-platform.test:8000/css/cssom-view/scroll-behavior-smooth-navigation.html:94:26
  │   │ Test.prototype.step@http://web-platform.test:8000/resources/testharness.js:2595:25
  └   └ smooth/window.onhashchange@http://web-platform.test:8000/css/cssom-view/scroll-behavior-smooth-navigation.html:92:35