[MSE][GStreamer] Make fake preroll asynchronous

[eocanha]

2a0710d

[MSE][GStreamer] Make fake preroll asynchronous
https://bugs.webkit.org/show_bug.cgi?id=295289

Reviewed by NOBODY (OOPS!).

With the current implementation the whole seek flow as executed in a single main loop cycle. As a result, the JS app had no chance to spot that video.seeking attribute is ever set to true. Also some apps listen to video.onseeking and expects that video.seeking attribute to be true in such case. That wasn't a valid assumption.

Also, the behaviour isn't the same in <video> elements that are audio-only as in <audio> elements.

This happens on the Amlogic platform, that doesn't have asynchronous state changes on its audio sink. Spotify is broken there because of this problem.

See:
WebPlatformForEmbedded/WPEWebKit#1232
WebPlatformForEmbedded/WPEWebKit#1527

This patch calls didPreroll() also for <video> elements that are audio-only. Also makes that call async by putting it on the HTML media element task queue to make sure it is executed after dispatching 'seeking' event to JS so the
app has a chance to notice that HTMLmedia.seeking attribute is 'true'.

Original author: Andrzej Surdej <[email protected]>

* Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.cpp:
(WebCore::MediaPlayerPrivateGStreamerMSE::doSeek): Find the actual final audio sink. Call didPreroll() asynchronously for any media element having only audio.

2a0710d

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
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	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 wpe-cairo
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[webkit-early-warning-system]

EWS run on previous version of this PR (hash c446216)

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 win
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	❌ 🧪 wpe-wk2	⏳ 🧪 win-tests
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 wpe-cairo
	✅ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
	✅ 🛠 vision	✅ 🧪 mac-AS-debug-wk2	❌ 🧪 gtk-wk2
	✅ 🛠 vision-sim	✅ 🧪 mac-wk2-stress	✅ 🧪 api-gtk
	✅ 🧪 vision-wk2	✅ 🧪 mac-intel-wk2	✅ 🛠 playstation
	✅ 🛠 tv	✅ 🛠 mac-safer-cpp
	✅ 🛠 tv-sim
	✅ 🛠 watch
	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash 2a0710d)

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 win
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2	⏳ 🧪 win-tests
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 wpe-cairo
	✅ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
	✅ 🛠 vision	✅ 🧪 mac-AS-debug-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 vision-sim	✅ 🧪 mac-wk2-stress	✅ 🧪 api-gtk
	✅ 🧪 vision-wk2	✅ 🧪 mac-intel-wk2	✅ 🛠 playstation
	✅ 🛠 tv	✅ 🛠 mac-safer-cpp
	✅ 🛠 tv-sim
	✅ 🛠 watch
	✅ 🛠 watch-sim