The following 2 layout tests:

media/track/track-webvtt-no-snap-to-lines-overlap.html
media/track/track-webvtt-snap-to-lines-left-right.html

are flaky crashes on macOS Debug queues.

HISTORY:

https://results.webkit.org/?suite=layout-tests&suite=layout-tests&test=media%2Ftrack%2Ftrack-webvtt-no-snap-to-lines-overlap.html&test=media%2Ftrack%2Ftrack-webvtt-snap-to-lines-left-right.html

STDERR TEXT:
ASSERTION FAILED: firstChild()
/Volumes/Data/worker/Apple-Ventura-Debug-Build/build/Source/WebCore/rendering/RenderVTTCue.cpp(79) : bool WebCore::RenderVTTCue::initializeLayoutParameters(WebCore::LayoutUnit &, WebCore::LayoutUnit &)
1   0x151cd6060 WTFCrash
2   0x107fd9fe0 WebCore::NetworkResourcesData::ResourceData::hasContent() const
3   0x1091c1bfc WebCore::RenderVTTCue::initializeLayoutParameters(WebCore::LayoutUnit&, WebCore::LayoutUnit&)
4   0x1091c17a8 WebCore::RenderVTTCue::repositionCueSnapToLinesSet()
5   0x1091c1730 WebCore::RenderVTTCue::layout()
6   0x108241714 WebCore::RenderElement::layoutIfNeeded()
7   0x108f70438 WebCore::RenderBlock::layoutPositionedObject(WebCore::RenderBox&, bool, bool)
8   0x108f6efa8 WebCore::RenderBlock::layoutPositionedObjects(bool, bool)
9   0x108f6eb2c WebCore::RenderBlock::simplifiedLayout()
10  0x108f89288 WebCore::RenderBlockFlow::layoutBlock(bool, WebCore::LayoutUnit)
11  0x108f6d164 WebCore::RenderBlock::layout()
12  0x108241714 WebCore::RenderElement::layoutIfNeeded()
13  0x108f70438 WebCore::RenderBlock::layoutPositionedObject(WebCore::RenderBox&, bool, bool)
14  0x108f6efa8 WebCore::RenderBlock::layoutPositionedObjects(bool, bool)
15  0x108f8995c WebCore::RenderBlockFlow::layoutBlock(bool, WebCore::LayoutUnit)
16  0x108f6d164 WebCore::RenderBlock::layout()
17  0x10907d870 WebCore::RenderImage::layoutShadowContent(WebCore::LayoutSize const&)
18  0x10907d450 WebCore::RenderImage::layout()
19  0x1091265d8 WebCore::RenderMedia::layout()
20  0x1091c3d80 WebCore::RenderVideo::layout()
21  0x108241714 WebCore::RenderElement::layoutIfNeeded()
22  0x108f8e378 WebCore::RenderBlockFlow::layoutModernLines(bool, WebCore::LayoutUnit&, WebCore::LayoutUnit&)
23  0x108f8bd70 WebCore::RenderBlockFlow::layoutInlineChildren(bool, WebCore::LayoutUnit&, WebCore::LayoutUnit&)
24  0x108f8a2b8 WebCore::RenderBlockFlow::layoutInFlowChildren(bool, WebCore::LayoutUnit&, WebCore::LayoutUnit&, WebCore::LayoutUnit&)
25  0x108f894b0 WebCore::RenderBlockFlow::layoutBlock(bool, WebCore::LayoutUnit)
26  0x108f6d164 WebCore::RenderBlock::layout()
27  0x108f8ce90 WebCore::RenderBlockFlow::layoutBlockChild(WebCore::RenderBox&, WebCore::RenderBlockFlow::MarginInfo&, WebCore::LayoutUnit&, WebCore::LayoutUnit&)
28  0x108f8c0d0 WebCore::RenderBlockFlow::layoutBlockChildren(bool, WebCore::LayoutUnit&)
29  0x108f8a2f4 WebCore::RenderBlockFlow::layoutInFlowChildren(bool, WebCore::LayoutUnit&, WebCore::LayoutUnit&, WebCore::LayoutUnit&)
30  0x108f894b0 WebCore::RenderBlockFlow::layoutBlock(bool, WebCore::LayoutUnit)
31  0x108f6d164 WebCore::RenderBlock::layout()
com.apple.WebKit.WebContent.Development terminated (pid 46474) for reason: crash
LEAK: 1 WebPageProxy