The following 9X imported css tests are all hitting the same assertion failure imported/w3c/web-platform-tests/css/css-view-transitions/animating-new-content-subset.html imported/w3c/web-platform-tests/css/css-view-transitions/content-with-transparent-background.html imported/w3c/web-platform-tests/css/css-view-transitions/massive-element-below-and-on-top-of-viewport-partially-onscreen-new.html imported/w3c/web-platform-tests/css/css-view-transitions/massive-element-below-viewport-offscreen-new.html imported/w3c/web-platform-tests/css/css-view-transitions/massive-element-below-viewport-partially-onscreen-old.html imported/w3c/web-platform-tests/css/css-view-transitions/massive-element-left-of-viewport-offscreen-new.html imported/w3c/web-platform-tests/css/css-view-transitions/massive-element-on-top-of-viewport-offscreen-new.html imported/w3c/web-platform-tests/css/css-view-transitions/offscreen-element-modified-before-coming-onscreen.html imported/w3c/web-platform-tests/css/css-view-transitions/span-with-overflowing-text-and-box-decorations.html HISTORY: https://results.webkit.org/?suite=layout-tests&suite=layout-tests&suite=layout-tests&suite=layout-tests&suite=layout-tests&suite=layout-tests&suite=layout-tests&suite=layout-tests&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcss-view-transitions%2Fcontent-with-transparent-background.html&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcss-view-transitions%2Fmassive-element-below-and-on-top-of-viewport-partially-onscreen-new.html&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcss-view-transitions%2Fmassive-element-below-viewport-offscreen-new.html&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcss-view-transitions%2Fmassive-element-below-viewport-partially-onscreen-old.html&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcss-view-transitions%2Fmassive-element-left-of-viewport-offscreen-new.html&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcss-view-transitions%2Fmassive-element-on-top-of-viewport-offscreen-new.html&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcss-view-transitions%2Foffscreen-element-modified-before-coming-onscreen.html&test=imported%2Fw3c%2Fweb-platform-tests%2Fcss%2Fcss-view-transitions%2Fspan-with-overflowing-text-and-box-decorations.html ASSERTION FAILED: willBeComposited == needsToBeComposited(layer, queryData) /Volumes/Data/worker/macOS-Sonoma-Debug-Build-EWS/build/Source/WebCore/rendering/RenderLayerCompositor.cpp(1256) : void WebCore::RenderLayerCompositor::computeCompositingRequirements(RenderLayer *, RenderLayer &, LayerOverlapMap &, CompositingState &, BackingSharingState &, bool &) com.apple.WebKit.WebContent.Development terminated (pid 27616) for reason: crash LEAK: 1 WebPageProxy
<rdar://problem/128558805>
These are flaky assertions, but so far evidence suggests that they only assert/crash when they are run together on the same worker.
Fixed by https://commits.webkit.org/279114@main
*** This bug has been marked as a duplicate of bug 274511 ***