MEDIA_ERR_ABORTED after restore page with media from bfcache

[pgorszkowski-igalia]

https://bugs.webkit.org/show_bug.cgi?id=319665

Reviewed by Alicia Boya Garcia and Nikolas Zimmermann.

This bundles three related fixes uncovered while restoring pages containing a media element (e.g.: "video") from the back/forward cache:

1. HTMLMediaElement::suspend() destroyed the media player on entering the cache (via stopWithoutDestroyingMediaPlayer() -> userCancelledLoad()), so a restored page reported video.error.code == MEDIA_ERR_ABORTED. userCancelledLoad() now takes a destroyMediaPlayer flag, false for the BackForwardCache suspension path, so it early-returns instead of tearing the player down.

2. A video that was playing before being cached did not resume playing after restore. HTMLMediaElement::resume() schedules an updatePlayState() task while the media session is still interrupted. mayResumePlayback() now also retries updatePlayState() when the element isn't paused.

3. A video that was paused before being cached showed a blank/white frame instead of its last decoded frame after restore. Restoring a page rebuilds the render tree, so CoordinatedPlatformLayerBufferProxy gets attached to a brand new CoordinatedPlatformLayer with no buffer of its own, and a paused GStreamer pipeline has no new sample to push. The proxy now invokes a layer-attached callback whenever a new non-null layer is attached, which MediaPlayerPrivateGStreamer uses to re-deliver its current sample so the new layer isn't left blank.

Also fixes a related macOS-only assert crash (ASSERTION FAILED: m_mediaSessions.contains(identifier) in MediaUsageManagerCocoa:: updateMediaUsage): the UI process unconditionally clears its usage-tracking map on every navigation commit, including a back/forward cache restore, but MediaElementSession kept believing it had already added its session across the whole suspend/resume cycle. mediaUsageManagerSessionWillBeSuspended() resets that flag on suspend so the next update re-adds the session first.

A LayoutTest for the playing-before-caching scenario (fix #2): it plays a video, waits for the playing event, navigates away and back via history.back(), and asserts the video is still not paused and currentTime has advanced after restore.

Added a LayoutTest based on media/restore-from-page-cache.html for a video that was paused before entering the cache, as a real pixel/screenshot comparison to catch the blank-frame regression from fix #3.

Tests: media/restore-from-page-cache-paused.html
media/restore-from-page-cache-playing.html

• LayoutTests/media/restore-from-page-cache-paused-expected.png: Added.
• LayoutTests/media/restore-from-page-cache-paused-expected.txt: Added.
• LayoutTests/media/restore-from-page-cache-paused.html: Added.
• LayoutTests/media/restore-from-page-cache-playing-expected.txt: Added.
• LayoutTests/media/restore-from-page-cache-playing.html: Added.
• LayoutTests/platform/ios/TestExpectations:
• Source/WebCore/html/HTMLMediaElement.cpp: (WebCore::HTMLMediaElement::userCancelledLoad):
  (WebCore::HTMLMediaElement::stopWithoutDestroyingMediaPlayer): (WebCore::HTMLMediaElement::suspend):
  (WebCore::HTMLMediaElement::mayResumePlayback):
• Source/WebCore/html/HTMLMediaElement.h:
• Source/WebCore/html/MediaElementSession.cpp: (WebCore::MediaElementSession::mediaUsageManagerSessionWillBeSuspended):
• Source/WebCore/html/MediaElementSession.h:
• Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp: (WebCore::MediaPlayerPrivateGStreamer::MediaPlayerPrivateGStreamer): (WebCore::MediaPlayerPrivateGStreamer::pushTextureToCompositor): (WebCore::MediaPlayerPrivateGStreamer::triggerRepaint):
• Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.h:
• Source/WebCore/platform/graphics/texmap/coordinated/CoordinatedPlatformLayerBufferProxy.cpp: (WebCore::CoordinatedPlatformLayerBufferProxy::CoordinatedPlatformLayerBufferProxy): (WebCore::CoordinatedPlatformLayerBufferProxy::create): (WebCore::CoordinatedPlatformLayerBufferProxy::setTargetLayer):
• Source/WebCore/platform/graphics/texmap/coordinated/CoordinatedPlatformLayerBufferProxy.h:

Canonical link: https://commits.webkit.org/319472@main

3a0c494

Build-Tests	Layout-Tests
✅ 🛠 wpe-246-amd64-build	✅ 🧪 wpe-246-amd64-layout
✅ 🛠 wpe-246-arm32-build	✅ 🧪 wpe-246-arm32-layout