REGRESSION(r277116?): [ macOS Release wk2 ] media/modern-media-controls/pip-support/pip-support-enabled.html (layout-test) is a flaky text failure

• Component: Media
• Status: NEW ---

[Robert Jenner]

media/modern-media-controls/pip-support/pip-support-enabled.html

is a flaky text failure on macOS Catalina and BigSur Release on wk2. 

HISTORY: 
https://results.webkit.org/?suite=layout-tests&test=media%2Fmodern-media-controls%2Fpip-support%2Fpip-support-enabled.html

TEXT DIFF:
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
 
-PASS mediaController.controls.pipButton.enabled is true
+FAIL mediaController.controls.pipButton.enabled should be true. Was false.
 PASS mediaController.controls.pipButton.enabled is false
 
 PASS successfullyParsed is true

https://build.webkit.org/results/Apple-BigSur-Release-WK2-Tests/r277172%20(2404)/media/modern-media-controls/pip-support/pip-support-enabled-pretty-diff.html

[Radar WebKit Bug Importer]

<rdar://problem/78024081>

[Robert Jenner]

Was able to reproduce the failing at BigSur Release ToT using the following test:

run-webkit-tests media/modern-media-controls/pip-support/pip-support-enabled.html --iterations 1000 -f

I was able to bisect this down having passed at r277112 and starting to fail at r277116. Looking through all of the commits between r277112 and r277116, it does look like changes at r277116 could potentially have caused this test to start flaky failing:
https://trac.webkit.org/changeset/277116/webkit

I have updated the test expectations to Pass Failure here:
https://trac.webkit.org/changeset/277625/webkit