There is a ASSERTION FAILED if we set the initial last reported size of ResizeObservation to -1 x -1, which is updated in the speciation, see https://github.com/WebKit/WebKit/pull/8839 If the initial size is 0x0, even ResizeObserver observe a disconnected target, it won't trigger ResizeObserver::deliverObservations. If the initial size is -1x-1, observing a disconnected target would trigger ResizeObserver::deliverObservations, then there we meet a ASSERTION FAILED. ResizeObserver needs a fix similar to https://bugs.webkit.org/show_bug.cgi?id=231235 stderr: ASSERTION FAILED: m_callback->hasCallback() page/ResizeObserver.cpp(145) : void WebCore::ResizeObserver::deliverObservations() 1 0x13a15a5e4 WTFCrash 2 0x2808333e0 WTFCrashWithInfo(int, char const*, char const*, int) 3 0x284c63440 WebCore::ResizeObserver::deliverObservations() 4 0x283aa9074 WebCore::Document::deliverResizeObservations() 5 0x283aa937c WebCore::Document::updateResizeObservations(WebCore::Page&) 6 0x284bd6850 WebCore::Page::updateRendering()::$_29::operator()(WebCore::Document&) const 7 0x284bd67cc WTF::Detail::CallableWrapper<WebCore::Page::updateRendering()::$_29, void, WebCore::Document&>::call(WebCore::Document&) 8 0x283cc64b0 WTF::Function<void (WebCore::Document&)>::operator()(WebCore::Document&) const 9 0x284b90688 WebCore::Page::forEachDocumentFromMainFrame(WebCore::Frame const&, WTF::Function<void (WebCore::Document&)> const&) 10 0x284b80840 WebCore::Page::forEachDocument(WTF::Function<void (WebCore::Document&)> const&) const 11 0x284b88468 WebCore::Page::updateRendering()::$_20::operator()(WebCore::RenderingUpdateStep, WTF::Function<void (WebCore::Document&)> const&) const 12 0x284b88134 WebCore::Page::updateRendering() 13 0x11d05eb10 WebKit::WebPage::updateRendering() 14 0x11c1d7b94 WebKit::TiledCoreAnimationDrawingArea::updateRendering(WebKit::TiledCoreAnimationDrawingArea::UpdateRenderingType)
Pull request: https://github.com/WebKit/WebKit/pull/9112
<rdar://problem/104822969>
Committed 259673@main (2861d8c4e29c): <https://commits.webkit.org/259673@main> Reviewed commits have been landed. Closing PR #9112 and removing active labels.
*** Bug 250836 has been marked as a duplicate of this bug. ***