[Gstreamer][WebRTC] webrtc/video-disabled-black.html fails

[philn]

aff28bc

[Gstreamer][WebRTC] webrtc/video-disabled-black.html fails
https://bugs.webkit.org/show_bug.cgi?id=254212

Reviewed by Xabier Rodriguez-Calvar.

Flushing a disabled video track would lead to a caps negotiation failure afterwards, so flush only
if the track is being re-enabled.

The webrtc/video-disabled-black.html test was also rewritten in order to avoid flakiness, we now
check the video at most 200 times instead of one, before failing the test.

Also drive-by in MediaStreamSource, rebuild black frame caps when needed, instead of attempting to
update caps that are not writable.

* LayoutTests/platform/glib/TestExpectations:
* LayoutTests/webrtc/routines.js:
* LayoutTests/webrtc/video-disabled-black.html:
* Source/WebCore/platform/mediastream/gstreamer/GStreamerMediaStreamSource.cpp:

Canonical link: https://commits.webkit.org/261951@main

8f8b6ee

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	⏳ 🛠 wpe	✅ 🛠 wincairo
⏳ 🧪 bindings	✅ 🛠 ios-sim	⏳ 🛠 mac-AS-debug	⏳ 🧪 wpe-wk2
✅ 🧪 webkitperl	⏳ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🛠 gtk
	⏳ 🧪 api-ios	✅ 🧪 mac-wk1	✅ 🧪 gtk-wk2
	✅ 🛠 tv	✅ 🧪 mac-wk2	✅ 🧪 api-gtk
	✅ 🛠 tv-sim	⏳ 🧪 mac-AS-debug-wk2
	✅ 🛠 watch	✅ 🧪 mac-wk2-stress
❌ 🛠 🧪 merge	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash 8f8b6ee)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	⏳ 🛠 wpe	✅ 🛠 wincairo
⏳ 🧪 bindings	✅ 🛠 ios-sim	⏳ 🛠 mac-AS-debug	⏳ 🧪 wpe-wk2
✅ 🧪 webkitperl	⏳ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🛠 gtk
	⏳ 🧪 api-ios	✅ 🧪 mac-wk1	✅ 🧪 gtk-wk2
	✅ 🛠 tv	✅ 🧪 mac-wk2	✅ 🧪 api-gtk
	✅ 🛠 tv-sim	⏳ 🧪 mac-AS-debug-wk2
	✅ 🛠 watch	✅ 🧪 mac-wk2-stress
❌ 🛠 🧪 merge	✅ 🛠 watch-sim

[webkit-commit-queue]

Committed 261951@main (aff28bc): https://commits.webkit.org/261951@main

Reviewed commits have been landed. Closing PR #11759 and removing active labels.