Seems like visualViewportEnabled is not enabled in iOS UIWebView (aka WebKitLegacy). ASSERTION FAILED: m_frame->settings().visualViewportEnabled() page/FrameView.cpp(5481) : WebCore::FloatRect WebCore::FrameView::absoluteToLayoutViewportRect(WebCore::FloatRect) const 1 0x12d5f6499 WTFCrash 2 0x1553e297b WTFCrashWithInfo(int, char const*, char const*, int) 3 0x159a3adac WebCore::FrameView::absoluteToLayoutViewportRect(WebCore::FloatRect) const 4 0x158c16462 WebCore::Document::updateIntersectionObservations() 5 0x159af0ed9 WebCore::Page::updateRendering()::$_30::operator()(WebCore::Document&) const 6 0x159af0e71 WTF::Detail::CallableWrapper<WebCore::Page::updateRendering()::$_30, void, WebCore::Document&>::call(WebCore::Document&) 7 0x158dfc6e7 WTF::Function<void (WebCore::Document&)>::operator()(WebCore::Document&) const 8 0x159ab744e WebCore::Page::forEachDocumentFromMainFrame(WebCore::Frame const&, WTF::Function<void (WebCore::Document&)> const&) 9 0x159aa6d15 WebCore::Page::forEachDocument(WTF::Function<void (WebCore::Document&)> const&) const 10 0x159aaeea3 WebCore::Page::updateRendering()::$_20::operator()(WebCore::RenderingUpdateStep, WTF::Function<void (WebCore::Document&)> const&) const 11 0x159aaeb3d WebCore::Page::updateRendering() 12 0x119731d87 -[WebView(WebViewInternal) _updateRendering] 13 0x1197342c4 WebViewRenderingUpdateScheduler::updateRendering() 14 0x1197341bf WebViewRenderingUpdateScheduler::renderingUpdateRunLoopObserverCallback() 15 0x11973f748 WebViewRenderingUpdateScheduler::WebViewRenderingUpdateScheduler(WebView*)::$_6::operator()() const 16 0x11973f6e9 WTF::Detail::CallableWrapper<WebViewRenderingUpdateScheduler::WebViewRenderingUpdateScheduler(WebView*)::$_6, void>::call() 17 0x155404232 WTF::Function<void ()>::operator()() const 18 0x159d78326 WebCore::RunLoopObserver::runLoopObserverFired() 19 0x159d7828d WebCore::RunLoopObserver::runLoopObserverFired(__CFRunLoopObserver*, unsigned long, void*) 20 0x10e2d40a5 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ 21 0x10e2cea12 __CFRunLoopDoObservers 22 0x10e2ce745 CFRunLoopRunSpecific 23 0x1579e6c04 RunWebThread(void*) 24 0x10e9a74e1 _pthread_start 25 0x10e9a2f6b thread_start (lldb)
<rdar://problem/103765638>