Bug 166008 – ASSERTION FAILED: willBeComposited == needsToBeComposited(layer) in WebCore::RenderLayerCompositor::computeCompositingRequirements

• Component: Layout and Rendering
• Status: NEW

[Renata Hodovan]

Load the attached test with sut.webkittestrunner:

Checked version: f368f1d
OS: Darwin-15.6.0-x86_64-i386-64bit

<style>{}*,*{transform:skew(152deg)skewY(58rad)translate(0);position:fixed</style><video controls>

Backtrace:

ASSERTION FAILED: willBeComposited == needsToBeComposited(layer)
WebKit/Source/WebCore/rendering/RenderLayerCompositor.cpp(1431) : void WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer *, WebCore::RenderLayer &, WebCore::RenderLayerCompositor::OverlapMap &, WebCore::RenderLayerCompositor::CompositingState &, bool &, bool &)
1   0x118aec4f1 WTFCrash
2   0x121fd97c1 WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer*, WebCore::RenderLayer&, WebCore::RenderLayerCompositor::OverlapMap&, WebCore::RenderLayerCompositor::CompositingState&, bool&, bool&)
3   0x121fd9636 WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer*, WebCore::RenderLayer&, WebCore::RenderLayerCompositor::OverlapMap&, WebCore::RenderLayerCompositor::CompositingState&, bool&, bool&)
4   0x121fd361f WebCore::RenderLayerCompositor::updateCompositingLayers(WebCore::CompositingUpdateType, WebCore::RenderLayer*)
5   0x11e8861e4 WebCore::FrameView::updateCompositingLayersAfterLayout()
6   0x11e88be17 WebCore::FrameView::layout(bool)
7   0x11df0b6fa WebCore::Document::updateLayout()
8   0x11df13fc1 WebCore::Document::updateLayoutIgnorePendingStylesheets(WebCore::Document::RunPostLayoutTasks)
9   0x11e2b3416 WebCore::Element::getBoundingClientRect()
10  0x11fdcd095 WebCore::jsElementPrototypeFunctionGetBoundingClientRect(JSC::ExecState*)
11  0x342a60601028
12  0x118171994 llint_entry
13  0x118171994 llint_entry
14  0x118171994 llint_entry
15  0x118171994 llint_entry
16  0x118171994 llint_entry
17  0x118171994 llint_entry
18  0x118171994 llint_entry
19  0x118171d05 llint_entry
20  0x11816a4ae vmEntryToJavaScript
21  0x117b982be JSC::JITCode::execute(JSC::VM*, JSC::ProtoCallFrame*)
22  0x117a636f1 JSC::Interpreter::executeCall(JSC::ExecState*, JSC::JSObject*, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&)
23  0x11654471b JSC::call(JSC::ExecState*, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&)
24  0x11ed613da WebCore::HTMLMediaElement::didAddUserAgentShadowRoot(WebCore::ShadowRoot*)
25  0x11e2b89a8 WebCore::Element::addShadowRoot(WTF::Ref<WebCore::ShadowRoot>&&)
26  0x11e2b8c7b WebCore::Element::ensureUserAgentShadowRoot()
27  0x11ed4f86a WebCore::HTMLMediaElement::ensureMediaControlsShadowRoot()
28  0x11ed291ed WebCore::HTMLMediaElement::configureMediaControls()
29  0x11ed2a886 WebCore::HTMLMediaElement::insertedInto(WebCore::ContainerNode&)
30  0x11d648184 WebCore::notifyNodeInsertedIntoDocument(WebCore::ContainerNode&, WebCore::Node&, WTF::Vector<WTF::Ref<WebCore::Node>, 11ul, WTF::CrashOnOverflow, 16ul>&)
31  0x11d648a44 WebCore::notifyChildNodeInserted(WebCore::ContainerNode&, WebCore::Node&, WTF::Vector<WTF::Ref<WebCore::Node>, 11ul, WTF::CrashOnOverflow, 16ul>&)
ASAN:DEADLYSIGNAL
=================================================================
==25428==ERROR: AddressSanitizer: SEGV on unknown address 0x0000bbadbeef (pc 0x000118aec529 bp 0x7fff509bdd50 sp 0x7fff509bdd40 T0)
    #0 0x118aec528 in WTFCrash (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2d01528)
    #1 0x121fd97c0 in WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer*, WebCore::RenderLayer&, WebCore::RenderLayerCompositor::OverlapMap&, WebCore::RenderLayerCompositor::CompositingState&, bool&, bool&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x52527c0)
    #2 0x121fd9635 in WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer*, WebCore::RenderLayer&, WebCore::RenderLayerCompositor::OverlapMap&, WebCore::RenderLayerCompositor::CompositingState&, bool&, bool&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x5252635)
    #3 0x121fd361e in WebCore::RenderLayerCompositor::updateCompositingLayers(WebCore::CompositingUpdateType, WebCore::RenderLayer*) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x524c61e)
    #4 0x11e8861e3 in WebCore::FrameView::updateCompositingLayersAfterLayout() (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1aff1e3)
    #5 0x11e88be16 in WebCore::FrameView::layout(bool) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1b04e16)
    #6 0x11df0b6f9 in WebCore::Document::updateLayout() (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x11846f9)
    #7 0x11df13fc0 in WebCore::Document::updateLayoutIgnorePendingStylesheets(WebCore::Document::RunPostLayoutTasks) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x118cfc0)
    #8 0x11e2b3415 in WebCore::Element::getBoundingClientRect() (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x152c415)
    #9 0x11fdcd094 in WebCore::jsElementPrototypeFunctionGetBoundingClientRect(JSC::ExecState*) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x3046094)
    #10 0x342a60601027  (<unknown module>)
    #11 0x118171993 in llint_entry (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2386993)
    #12 0x118171993 in llint_entry (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2386993)
    #13 0x118171993 in llint_entry (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2386993)
    #14 0x118171993 in llint_entry (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2386993)
    #15 0x118171993 in llint_entry (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2386993)
    #16 0x118171993 in llint_entry (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2386993)
    #17 0x118171993 in llint_entry (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2386993)
    #18 0x118171d04 in llint_entry (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2386d04)
    #19 0x11816a4ad in vmEntryToJavaScript (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x237f4ad)
    #20 0x117b982bd in JSC::JITCode::execute(JSC::VM*, JSC::ProtoCallFrame*) (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x1dad2bd)
    #21 0x117a636f0 in JSC::Interpreter::executeCall(JSC::ExecState*, JSC::JSObject*, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x1c786f0)
    #22 0x11654471a in JSC::call(JSC::ExecState*, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x75971a)
    #23 0x11ed613d9 in WebCore::HTMLMediaElement::didAddUserAgentShadowRoot(WebCore::ShadowRoot*) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1fda3d9)
    #24 0x11e2b89a7 in WebCore::Element::addShadowRoot(WTF::Ref<WebCore::ShadowRoot>&&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x15319a7)
    #25 0x11e2b8c7a in WebCore::Element::ensureUserAgentShadowRoot() (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1531c7a)
    #26 0x11ed4f869 in WebCore::HTMLMediaElement::ensureMediaControlsShadowRoot() (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1fc8869)
    #27 0x11ed291ec in WebCore::HTMLMediaElement::configureMediaControls() (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1fa21ec)
    #28 0x11ed2a885 in WebCore::HTMLMediaElement::insertedInto(WebCore::ContainerNode&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1fa3885)
    #29 0x11d648183 in WebCore::notifyNodeInsertedIntoDocument(WebCore::ContainerNode&, WebCore::Node&, WTF::Vector<WTF::Ref<WebCore::Node>, 11ul, WTF::CrashOnOverflow, 16ul>&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x8c1183)
    #30 0x11d648a43 in WebCore::notifyChildNodeInserted(WebCore::ContainerNode&, WebCore::Node&, WTF::Vector<WTF::Ref<WebCore::Node>, 11ul, WTF::CrashOnOverflow, 16ul>&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x8c1a43)
    #31 0x11d6251a9 in WebCore::ContainerNode::notifyChildInserted(WebCore::Node&, WebCore::ContainerNode::ChildChangeSource) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x89e1a9)
    #32 0x11d62370d in WebCore::ContainerNode::parserAppendChild(WebCore::Node&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x89c70d)
    #33 0x11ebc42c2 in WebCore::insert(WebCore::HTMLConstructionSiteTask&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1e3d2c2)
    #34 0x11ebc3d6e in WebCore::executeInsertTask(WebCore::HTMLConstructionSiteTask&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1e3cd6e)
    #35 0x11ebbcbc1 in WebCore::executeTask(WebCore::HTMLConstructionSiteTask&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1e35bc1)
    #36 0x11ebbca98 in WebCore::HTMLConstructionSite::executeQueuedTasks() (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1e35a98)
    #37 0x11eea46a2 in WebCore::HTMLTreeBuilder::constructTree(WebCore::AtomicHTMLToken&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x211d6a2)
    #38 0x11ec30576 in WebCore::HTMLDocumentParser::constructTreeFromHTMLToken(WebCore::HTMLTokenizer::TokenPtr&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1ea9576)
    #39 0x11ec302d2 in WebCore::HTMLDocumentParser::pumpTokenizerLoop(WebCore::HTMLDocumentParser::SynchronousMode, bool, WebCore::PumpSession&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1ea92d2)
    #40 0x11ec2deb2 in WebCore::HTMLDocumentParser::pumpTokenizer(WebCore::HTMLDocumentParser::SynchronousMode) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1ea6eb2)
    #41 0x11ec2d86f in WebCore::HTMLDocumentParser::pumpTokenizerIfPossible(WebCore::HTMLDocumentParser::SynchronousMode) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1ea686f)
    #42 0x11ec31afb in WebCore::HTMLDocumentParser::append(WTF::RefPtr<WTF::StringImpl>&&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1eaaafb)
    #43 0x11dddf1eb in WebCore::DecodedDataDocumentParser::appendBytes(WebCore::DocumentWriter&, char const*, unsigned long) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x10581eb)
    #44 0x11e0fdcf1 in WebCore::DocumentWriter::addData(char const*, unsigned long) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x1376cf1)
    #45 0x11e058045 in WebCore::DocumentLoader::commitData(char const*, unsigned long) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x12d1045)
    #46 0x110342e4d in WebKit::WebFrameLoaderClient::committedLoad(WebCore::DocumentLoader*, char const*, int) (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/WebKit+0x10ede4d)
    #47 0x11e05d1b6 in WebCore::DocumentLoader::commitLoad(char const*, int) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x12d61b6)
    #48 0x11e05cefa in WebCore::DocumentLoader::dataReceived(char const*, int) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x12d5efa)
    #49 0x11e05d598 in WebCore::DocumentLoader::dataReceived(WebCore::CachedResource&, char const*, int) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x12d6598)
    #50 0x11d38d931 in WebCore::CachedRawResource::notifyClientsDataWasReceived(char const*, unsigned int) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x606931)
    #51 0x11d38d5e0 in WebCore::CachedRawResource::addDataBuffer(WebCore::SharedBuffer&) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x6065e0)
    #52 0x122e8991a in WebCore::SubresourceLoader::didReceiveDataOrBuffer(char const*, int, WTF::RefPtr<WebCore::SharedBuffer>&&, long long, WebCore::DataPayloadType) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x610291a)
    #53 0x122e89250 in WebCore::SubresourceLoader::didReceiveData(char const*, unsigned int, long long, WebCore::DataPayloadType) (WebKit/WebKitBuild/Debug/WebCore.framework/Versions/A/WebCore+0x6102250)
    #54 0x110ce61fa in WebKit::WebResourceLoader::didReceiveData(IPC::DataReference const&, long long) (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/WebKit+0x1a911fa)
    #55 0x110cf4003 in void IPC::callMemberFunctionImpl<WebKit::WebResourceLoader, void (WebKit::WebResourceLoader::*)(IPC::DataReference const&, long long), std::__1::tuple<IPC::DataReference, long long>, 0ul, 1ul>(WebKit::WebResourceLoader*, void (WebKit::WebResourceLoader::*)(IPC::DataReference const&, long long), std::__1::tuple<IPC::DataReference, long long>&&, std::__1::integer_sequence<unsigned long, 0ul, 1ul>) (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/WebKit+0x1a9f003)
    #56 0x110cf3b04 in void IPC::callMemberFunction<WebKit::WebResourceLoader, void (WebKit::WebResourceLoader::*)(IPC::DataReference const&, long long), std::__1::tuple<IPC::DataReference, long long>, std::__1::integer_sequence<unsigned long, 0ul, 1ul> >(std::__1::tuple<IPC::DataReference, long long>&&, WebKit::WebResourceLoader*, void (WebKit::WebResourceLoader::*)(IPC::DataReference const&, long long)) (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/WebKit+0x1a9eb04)
    #57 0x110cf1211 in void IPC::handleMessage<Messages::WebResourceLoader::DidReceiveData, WebKit::WebResourceLoader, void (WebKit::WebResourceLoader::*)(IPC::DataReference const&, long long)>(IPC::Decoder&, WebKit::WebResourceLoader*, void (WebKit::WebResourceLoader::*)(IPC::DataReference const&, long long)) (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/WebKit+0x1a9c211)
    #58 0x110cef7c0 in WebKit::WebResourceLoader::didReceiveWebResourceLoaderMessage(IPC::Connection&, IPC::Decoder&) (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/WebKit+0x1a9a7c0)
    #59 0x10fa18da9 in WebKit::NetworkProcessConnection::didReceiveMessage(IPC::Connection&, IPC::Decoder&) (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/WebKit+0x7c3da9)
    #60 0x10f42cfba in IPC::Connection::dispatchMessage(IPC::Decoder&) (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/WebKit+0x1d7fba)
    #61 0x10f4157c4 in IPC::Connection::dispatchMessage(std::__1::unique_ptr<IPC::Decoder, std::__1::default_delete<IPC::Decoder> >) (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/WebKit+0x1c07c4)
    #62 0x10f42dca5 in IPC::Connection::dispatchOneMessage() (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/WebKit+0x1d8ca5)
    #63 0x10f43e25c in IPC::Connection::enqueueIncomingMessage(std::__1::unique_ptr<IPC::Decoder, std::__1::default_delete<IPC::Decoder> >)::$_14::operator()() (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/WebKit+0x1e925c)
    #64 0x10f43e188 in WTF::Function<void ()>::CallableWrapper<IPC::Connection::enqueueIncomingMessage(std::__1::unique_ptr<IPC::Decoder, std::__1::default_delete<IPC::Decoder> >)::$_14>::call() (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/WebKit+0x1e9188)
    #65 0x118b70830 in WTF::Function<void ()>::operator()() const (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2d85830)
    #66 0x118bbac46 in WTF::RunLoop::performWork() (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2dcfc46)
    #67 0x118bbbb11 in WTF::RunLoop::performWork(void*) (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2dd0b11)
    #68 0x7fff81c1f880 in __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ (/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation+0xaa880)
    #69 0x7fff81bfefbb in __CFRunLoopDoSources0 (/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation+0x89fbb)
    #70 0x7fff81bfe4de in __CFRunLoopRun (/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation+0x894de)
    #71 0x7fff81bfded7 in CFRunLoopRunSpecific (/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation+0x88ed7)
    #72 0x7fff82fde934 in RunCurrentEventLoopInMode (/System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/HIToolbox.framework/Versions/A/HIToolbox+0x30934)
    #73 0x7fff82fde76e in ReceiveNextEventCommon (/System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/HIToolbox.framework/Versions/A/HIToolbox+0x3076e)
    #74 0x7fff82fde5ae in _BlockUntilNextEventMatchingListInModeWithFilter (/System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/HIToolbox.framework/Versions/A/HIToolbox+0x305ae)
    #75 0x7fff8e643df5 in _DPSNextEvent (/System/Library/Frameworks/AppKit.framework/Versions/C/AppKit+0x48df5)
    #76 0x7fff8e643225 in -[NSApplication _nextEventMatchingEventMask:untilDate:inMode:dequeue:] (/System/Library/Frameworks/AppKit.framework/Versions/C/AppKit+0x48225)
    #77 0x7fff8e637d7f in -[NSApplication run] (/System/Library/Frameworks/AppKit.framework/Versions/C/AppKit+0x3cd7f)
    #78 0x7fff8e601367 in NSApplicationMain (/System/Library/Frameworks/AppKit.framework/Versions/C/AppKit+0x6367)
    #79 0x7fff92f09193 in _xpc_objc_main (/usr/lib/system/libxpc.dylib+0x11193)
    #80 0x7fff92f07bbd in xpc_main (/usr/lib/system/libxpc.dylib+0xfbbd)
    #81 0x10f239f73 in main (WebKit/WebKitBuild/Debug/WebKit.framework/Versions/A/XPCServices/com.apple.WebKit.WebContent.xpc/Contents/MacOS/com.apple.WebKit.WebContent.Development+0x100001f73)
    #82 0x7fff8ab8d5ac in start (/usr/lib/system/libdyld.dylib+0x35ac)
    #83 0x0  (<unknown module>)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV (WebKit/WebKitBuild/Debug/JavaScriptCore.framework/Versions/A/JavaScriptCore+0x2d01528) in WTFCrash
==25428==ABORTING
#CRASHED - com.apple.WebKit.WebContent.Development (pid 25428)

[Renata Hodovan]

Created attachment 297434 [details]
Test

[Simon Fraser (smfr)]

This is caused by media script running in the middle of tree building.

[alan]

(In reply to comment #2)
> This is caused by media script running in the middle of tree building.
Moar assertions!

[Antoine Quint]

I wonder if this applies to modern media controls where most of the DOM changes are performed asynchronously.

[Alicia Boya García]

This is assertion error is still an issue.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Dash.js player</title>
    <style>
        html, body {
            margin: 0;
            padding: 0;
            overflow: hidden;
            background: #6f8742;
        }
        body {
            position: absolute;
            top: 0;
            bottom: 0;
            left: 0;
            right: 0;
        }
        #video {
            width: 100%;
            height: 100%;
        }
    </style>
</head>
<body>
<script src="https://cdnjs.cloudflare.com/ajax/libs/dashjs/2.9.2/dash.all.debug.js"></script>
<video data-dashjs-player autoplay controls id="video" src="http://www-itec.uni-klu.ac.at/ftp/datasets/DASHDataset2014/BigBuckBunny/15sec/BigBuckBunny_15s_onDemand_2014_05_09.mpd"></video>
</body>
</html>

Note: The URL does not load (CORS problem I guess). It doesn't matter. It will crash when you move the mouse over the window nevertheless.

[Alicia Boya García]

ASSERTION FAILED: willBeComposited == needsToBeComposited(layer, queryData)

[Current thread is 1 (Thread 0x7fdbaff1aac0 (LWP 25450))]
Missing separate debuginfos, use: dnf debuginfo-install elfutils-libelf-0.174-5.fc29.x86_64 glibc-2.28-23.fc29.x86_64 nettle-3.4.1rc1-1.fc29.x86_64
(gdb) bt
#0  WTFCrash () at ../../Source/WTF/wtf/Assertions.cpp:255
#1  0x00007fdbc99c771c in WebCore::RenderLayerCompositor::computeCompositingRequirements (this=0x7fdbaf569d40, ancestorLayer=0x7fdbaf5a3b40, layer=..., overlapMap=..., compositingState=..., 
    descendantHas3DTransform=@0x7fffa305cbef: false) at ../../Source/WebCore/rendering/RenderLayerCompositor.cpp:983
#2  0x00007fdbc99c72ca in WebCore::RenderLayerCompositor::computeCompositingRequirements (this=0x7fdbaf569d40, ancestorLayer=0x7fdbaf5a38c0, layer=..., overlapMap=..., compositingState=..., 
    descendantHas3DTransform=@0x7fffa305cd3f: false) at ../../Source/WebCore/rendering/RenderLayerCompositor.cpp:901
#3  0x00007fdbc99c72ca in WebCore::RenderLayerCompositor::computeCompositingRequirements (this=0x7fdbaf569d40, ancestorLayer=0x0, layer=..., overlapMap=..., compositingState=..., 
    descendantHas3DTransform=@0x7fffa305d30f: false) at ../../Source/WebCore/rendering/RenderLayerCompositor.cpp:901
#4  0x00007fdbc99c67ac in WebCore::RenderLayerCompositor::updateCompositingLayers (this=0x7fdbaf569d40, updateType=WebCore::CompositingUpdateType::AfterLayout, updateRoot=0x7fdbaf5a38c0)
    at ../../Source/WebCore/rendering/RenderLayerCompositor.cpp:729
#5  0x00007fdbc9403b43 in WebCore::FrameView::updateCompositingLayersAfterLayout (this=0x7fdb508004e0) at ../../Source/WebCore/page/FrameView.cpp:850
#6  0x00007fdbc9404ff0 in WebCore::FrameView::didLayout (this=0x7fdb508004e0, layoutRoot=...) at ../../Source/WebCore/page/FrameView.cpp:1300
#7  0x00007fdbc943d91c in WebCore::FrameViewLayoutContext::layout (this=0x7fdb508008f8) at ../../Source/WebCore/page/FrameViewLayoutContext.cpp:239
#8  0x00007fdbc8c63ee4 in WebCore::Document::updateLayout (this=0x7fdb50600ff0) at ../../Source/WebCore/dom/Document.cpp:2093
#9  0x00007fdbc8c63f6e in WebCore::Document::updateLayoutIgnorePendingStylesheets (this=0x7fdb50600ff0, runPostLayoutTasks=WebCore::Document::RunPostLayoutTasks::Asynchronously)
    at ../../Source/WebCore/dom/Document.cpp:2107
#10 0x00007fdbc8ce9b14 in WebCore::Element::offsetLeft (this=0x7fdb32c000f0) at ../../Source/WebCore/dom/Element.cpp:888
#11 0x00007fdbc7d0ba77 in WebCore::jsHTMLElementOffsetLeftGetter (state=..., thisObject=..., throwScope=...) at DerivedSources/WebCore/JSHTMLElement.cpp:966
#12 0x00007fdbc7d17d52 in WebCore::IDLAttribute<WebCore::JSHTMLElement>::get<WebCore::jsHTMLElementOffsetLeftGetter, (WebCore::CastedThisErrorBehavior)3> (state=..., thisValue=140579613835264, 
    attributeName=0x7fdbcb82e0a0 "offsetLeft") at ../../Source/WebCore/bindings/js/JSDOMAttribute.h:69
#13 0x00007fdbc7d0bacf in WebCore::jsHTMLElementOffsetLeft (state=0x7fffa305dc00, thisValue=140579613835264) at DerivedSources/WebCore/JSHTMLElement.cpp:972
#14 0x00007fdbbc8840b1 in JSC::PropertySlot::customGetter (this=0x7fffa305da30, exec=0x7fffa305dc00, propertyName=...) at ../../Source/JavaScriptCore/runtime/PropertySlot.cpp:50
#15 0x00007fdbc78da97f in JSC::PropertySlot::getValue (this=0x7fffa305da30, exec=0x7fffa305dc00, propertyName=...) at DerivedSources/ForwardingHeaders/JavaScriptCore/PropertySlot.h:410
#16 0x00007fdbbbf97a31 in JSC::JSValue::get (this=0x7fffa305da88, exec=0x7fffa305dc00, propertyName=..., slot=...) at ../../Source/JavaScriptCore/runtime/JSCJSValueInlines.h:841
#17 0x00007fdbbc56610a in JSC::LLInt::llint_slow_path_get_by_id (exec=0x7fffa305dc00, pc=0x7fdb3e6e328f) at ../../Source/JavaScriptCore/llint/LLIntSlowPaths.cpp:764
#18 0x00007fdbbc5555f5 in llint_entry () from /webkit/WebKitBuild/Debug/lib/libjavascriptcoregtk-4.0.so.18
#19 0x00007fdbbc560073 in llint_entry () from /webkit/WebKitBuild/Debug/lib/libjavascriptcoregtk-4.0.so.18
#20 0x00007fdbbc560073 in llint_entry () from /webkit/WebKitBuild/Debug/lib/libjavascriptcoregtk-4.0.so.18
#21 0x00007fdbbc5600fd in llint_entry () from /webkit/WebKitBuild/Debug/lib/libjavascriptcoregtk-4.0.so.18
#22 0x00007fdbbc54e988 in vmEntryToJavaScript () from /webkit/WebKitBuild/Debug/lib/libjavascriptcoregtk-4.0.so.18
#23 0x00007fdbbc48e8ad in JSC::JITCode::execute (this=0x7fdb3e6d7168, vm=0x7fdb60000000, protoCallFrame=0x7fffa305dfa0) at ../../Source/JavaScriptCore/jit/JITCodeInlines.h:38
#24 0x00007fdbbc486392 in JSC::Interpreter::executeCall (this=0x7fdbaf5ff790, callFrame=0x7fdb534e0ff8, function=0x7fdb3df50600, callType=JSC::CallType::JS, callData=..., thisValue=..., args=...)
    at ../../Source/JavaScriptCore/interpreter/Interpreter.cpp:891
#25 0x00007fdbbc6cb238 in JSC::call (exec=0x7fdb534e0ff8, functionObject=..., callType=JSC::CallType::JS, callData=..., thisValue=..., args=...) at ../../Source/JavaScriptCore/runtime/CallData.cpp:41
#26 0x00007fdbbc6cb309 in JSC::call (exec=0x7fdb534e0ff8, functionObject=..., callType=JSC::CallType::JS, callData=..., thisValue=..., args=..., returnedException=...)
    at ../../Source/JavaScriptCore/runtime/CallData.cpp:48
#27 0x00007fdbbc6cb4c5 in JSC::profiledCall (exec=0x7fdb534e0ff8, reason=JSC::ProfilingReason::Other, functionObject=..., callType=JSC::CallType::JS, callData=..., thisValue=..., args=..., 
    returnedException=...) at ../../Source/JavaScriptCore/runtime/CallData.cpp:69
#28 0x00007fdbc88b5870 in WebCore::JSExecState::profiledCall (exec=0x7fdb534e0ff8, reason=JSC::ProfilingReason::Other, functionObject=..., callType=JSC::CallType::JS, callData=..., thisValue=..., args=..., 
    returnedException=...) at ../../Source/WebCore/bindings/js/JSExecState.h:74
#29 0x00007fdbc88ea731 in WebCore::JSEventListener::handleEvent (this=0x7fdb3e03cf88, scriptExecutionContext=..., event=...) at ../../Source/WebCore/bindings/js/JSEventListener.cpp:175
#30 0x00007fdbc8d15e0b in WebCore::EventTarget::innerInvokeEventListeners (this=0x7fdb3c4008d0, event=..., listeners=..., phase=WebCore::EventTarget::EventInvokePhase::Bubbling)
    at ../../Source/WebCore/dom/EventTarget.cpp:301
#31 0x00007fdbc8d15928 in WebCore::EventTarget::fireEventListeners (this=0x7fdb3c4008d0, event=..., phase=WebCore::EventTarget::EventInvokePhase::Bubbling) at ../../Source/WebCore/dom/EventTarget.cpp:242
#32 0x00007fdbc8d60b2b in WebCore::Node::handleLocalEvents (this=0x7fdb3c4008d0, event=..., phase=WebCore::EventTarget::EventInvokePhase::Bubbling) at ../../Source/WebCore/dom/Node.cpp:2374
#33 0x00007fdbc8cf8ec3 in WebCore::EventContext::handleLocalEvents (this=0x7fd9401fffa0, event=..., phase=WebCore::EventTarget::EventInvokePhase::Bubbling) at ../../Source/WebCore/dom/EventContext.cpp:55
#34 0x00007fdbc8d0f6f6 in WebCore::dispatchEventInDOM (event=..., path=...) at ../../Source/WebCore/dom/EventDispatcher.cpp:100
#35 0x00007fdbc8d0fb19 in WebCore::EventDispatcher::dispatchEvent (node=..., event=...) at ../../Source/WebCore/dom/EventDispatcher.cpp:154
#36 0x00007fdbc8d60b7d in WebCore::Node::dispatchEvent (this=0x7fdb3c4008d0, event=...) at ../../Source/WebCore/dom/Node.cpp:2384
#37 0x00007fdbc8d20059 in WebCore::GenericEventQueue::dispatchOneEvent (this=0x7fdb3c400e40) at ../../Source/WebCore/dom/GenericEventQueue.cpp:73
#38 0x00007fdbc8d2cbb6 in std::__invoke_impl<void, void (WebCore::GenericEventQueue::*&)(), WebCore::GenericEventQueue*&> (
    __f=@0x7fd94017d488: (void (WebCore::GenericEventQueue::*)(WebCore::GenericEventQueue * const)) 0x7fdbc8d1fe4c <WebCore::GenericEventQueue::dispatchOneEvent()>, __t=@0x7fd94017d498: 0x7fdb3c400e40)
    at /usr/include/c++/8/bits/invoke.h:73
#39 0x00007fdbc8d2cb2d in std::__invoke<void (WebCore::GenericEventQueue::*&)(), WebCore::GenericEventQueue*&> (
    __fn=@0x7fd94017d488: (void (WebCore::GenericEventQueue::*)(WebCore::GenericEventQueue * const)) 0x7fdbc8d1fe4c <WebCore::GenericEventQueue::dispatchOneEvent()>, __args#0=@0x7fd94017d498: 0x7fdb3c400e40)
--Type <RET> for more, q to quit, c to continue without paging--
    at /usr/include/c++/8/bits/invoke.h:95
#40 0x00007fdbc8d2ca9a in std::_Bind<void (WebCore::GenericEventQueue::*(WebCore::GenericEventQueue*))()>::__call<void, , 0ul>(std::tuple<>&&, std::_Index_tuple<0ul>) (this=0x7fd94017d488, __args=...)
    at /usr/include/c++/8/functional:400
#41 0x00007fdbc8d2ca50 in std::_Bind<void (WebCore::GenericEventQueue::*(WebCore::GenericEventQueue*))()>::operator()<, void>() (this=0x7fd94017d488) at /usr/include/c++/8/functional:484
#42 0x00007fdbc8d2ca2a in WTF::Function<void ()>::CallableWrapper<std::_Bind<void (WebCore::GenericEventQueue::*(WebCore::GenericEventQueue*))()> >::call() (this=0x7fd94017d480)
    at DerivedSources/ForwardingHeaders/wtf/Function.h:101
#43 0x00007fdbc703af42 in WTF::Function<void ()>::operator()() const (this=0x7fd94015ac40) at DerivedSources/ForwardingHeaders/wtf/Function.h:56
#44 0x00007fdbc86843d4 in WebCore::GenericTaskQueue<WebCore::Timer, unsigned int>::enqueueTask(WTF::Function<void ()>&&)::{lambda()#1}::operator()() const (this=0x7fd94015ac38)
    at ../../Source/WebCore/platform/GenericTaskQueue.h:106
#45 0x00007fdbc8686f4a in WTF::Function<void ()>::CallableWrapper<WebCore::GenericTaskQueue<WebCore::Timer, unsigned int>::enqueueTask(WTF::Function<void ()>&&)::{lambda()#1}>::call() (this=0x7fd94015ac30)
    at DerivedSources/ForwardingHeaders/wtf/Function.h:101
#46 0x00007fdbc703af42 in WTF::Function<void ()>::operator()() const (this=0x7fffa305eb60) at DerivedSources/ForwardingHeaders/wtf/Function.h:56
#47 0x00007fdbc954f93f in WebCore::TaskDispatcher<WebCore::Timer>::dispatchOneTask (this=0x7fdb3c400e50) at ../../Source/WebCore/platform/GenericTaskQueue.cpp:110
#48 0x00007fdbc954f7ee in WebCore::TaskDispatcher<WebCore::Timer>::sharedTimerFired () at ../../Source/WebCore/platform/GenericTaskQueue.cpp:85
#49 0x00007fdbc954f631 in WebCore::TaskDispatcher<WebCore::Timer>::<lambda()>::operator()(void) const (__closure=0x7fdb3e070748) at ../../Source/WebCore/platform/GenericTaskQueue.cpp:60
#50 0x00007fdbc9550928 in WTF::Function<void()>::CallableWrapper<WebCore::TaskDispatcher<WebCore::Timer>::sharedTimer()::<lambda()> >::call(void) (this=0x7fdb3e070740)
    at DerivedSources/ForwardingHeaders/wtf/Function.h:101
#51 0x00007fdbc703af42 in WTF::Function<void ()>::operator()() const (this=0x7fdbcfd17438 <WebCore::TaskDispatcher<WebCore::Timer>::sharedTimer()::timer+56>)
    at DerivedSources/ForwardingHeaders/wtf/Function.h:56
#52 0x00007fdbc7037f1e in WebCore::Timer::fired (this=0x7fdbcfd17400 <WebCore::TaskDispatcher<WebCore::Timer>::sharedTimer()::timer>) at ../../Source/WebCore/platform/Timer.h:131
#53 0x00007fdbc957c3fe in WebCore::ThreadTimers::sharedTimerFiredInternal (this=0x7fdbaf588e60) at ../../Source/WebCore/platform/ThreadTimers.cpp:117
#54 0x00007fdbc957bf5b in WebCore::ThreadTimers::<lambda()>::operator()(void) const (__closure=0x7fdbaf5fa3d8) at ../../Source/WebCore/platform/ThreadTimers.cpp:69
#55 0x00007fdbc957fb18 in WTF::Function<void()>::CallableWrapper<WebCore::ThreadTimers::setSharedTimer(WebCore::SharedTimer*)::<lambda()> >::call(void) (this=0x7fdbaf5fa3d0)
    at DerivedSources/ForwardingHeaders/wtf/Function.h:101
#56 0x00007fdbc703af42 in WTF::Function<void ()>::operator()() const (this=0x7fdbcfd17748 <WebCore::MainThreadSharedTimer::singleton()::instance+8>) at DerivedSources/ForwardingHeaders/wtf/Function.h:56
#57 0x00007fdbc955e101 in WebCore::MainThreadSharedTimer::fired (this=0x7fdbcfd17740 <WebCore::MainThreadSharedTimer::singleton()::instance>) at ../../Source/WebCore/platform/MainThreadSharedTimer.cpp:83
#58 0x00007fdbc9561efa in WTF::RunLoop::Timer<WebCore::MainThreadSharedTimer>::fired (this=0x7fdbcfd17750 <WebCore::MainThreadSharedTimer::singleton()::instance+16>)
    at DerivedSources/ForwardingHeaders/wtf/RunLoop.h:148
#59 0x00007fdbbcb6214b in WTF::RunLoop::TimerBase::<lambda(gpointer)>::operator()(gpointer) const (__closure=0x0, userData=0x7fdbcfd17750 <WebCore::MainThreadSharedTimer::singleton()::instance+16>)
    at ../../Source/WTF/wtf/glib/RunLoopGLib.cpp:170
#60 0x00007fdbbcb621a3 in WTF::RunLoop::TimerBase::<lambda(gpointer)>::_FUN(gpointer) () at ../../Source/WTF/wtf/glib/RunLoopGLib.cpp:176
#61 0x00007fdbbcb618c8 in WTF::<lambda(GSource*, GSourceFunc, gpointer)>::operator()(GSource *, GSourceFunc, gpointer) const (__closure=0x0, source=0x2827a60, 
    callback=0x7fdbbcb62186 <WTF::RunLoop::TimerBase::<lambda(gpointer)>::_FUN(gpointer)>, userData=0x7fdbcfd17750 <WebCore::MainThreadSharedTimer::singleton()::instance+16>)
    at ../../Source/WTF/wtf/glib/RunLoopGLib.cpp:45
#62 0x00007fdbbcb618f8 in WTF::<lambda(GSource*, GSourceFunc, gpointer)>::_FUN(GSource *, GSourceFunc, gpointer) () at ../../Source/WTF/wtf/glib/RunLoopGLib.cpp:46
#63 0x00007fdbb3fdb818 in g_main_dispatch () at /webkit/WebKitBuild/DependenciesGTK/Source/glib-2.54.2/glib/gmain.c:3148
#64 g_main_context_dispatch () at /webkit/WebKitBuild/DependenciesGTK/Source/glib-2.54.2/glib/gmain.c:3813
#65 0x00007fdbb3fdbbd8 in g_main_context_iterate () at /webkit/WebKitBuild/DependenciesGTK/Source/glib-2.54.2/glib/gmain.c:3886
#66 0x00007fdbb3fdbec2 in g_main_loop_run () at /webkit/WebKitBuild/DependenciesGTK/Source/glib-2.54.2/glib/gmain.c:4082
#67 0x00007fdbbcb61e06 in WTF::RunLoop::run () at ../../Source/WTF/wtf/glib/RunLoopGLib.cpp:96
#68 0x00007fdbc7a3ca71 in WebKit::ChildProcessMain<WebKit::WebProcess, WebKit::WebProcessMain> (argc=3, argv=0x7fffa305f118) at ../../Source/WebKit/Shared/unix/ChildProcessMain.h:61
#69 0x00007fdbc7a3a34f in WebKit::WebProcessMainUnix (argc=3, argv=0x7fffa305f118) at ../../Source/WebKit/WebProcess/gtk/WebProcessMainGtk.cpp:67
#70 0x0000000000400cc1 in main (argc=3, argv=0x7fffa305f118) at ../../Source/WebKit/WebProcess/EntryPoint/unix/WebProcessMain.cpp:52

[Daniel Bates]

Just hit this bug today with a debug build at r239512 on <https://vrbo.com> while looking into <rdar://problem/46863949>. It was triggered from accessibility code. Here are the steps I performed:

1. Visit <https://vrbo.com>.
2. Focus the Destination field and pick someplace.
3. After selecting a destination, the Arrive field is automatically focused. Pick a date.
4. Same as 3 but with the Depart field.
5. Scroll the page up.

Then the WebContent process crashed due to the ASSERT(willBeComposited == needsToBeComposited(layer, queryData)); failing in RenderLayerCompositor::computeCompositingRequirements(). Here is the backtrace:

#0  0x00000007bec304e0 in ::WTFCrash() at /Volumes/.../OpenSource/Source/WTF/wtf/Assertions.cpp:255
#1  0x00000007a800daeb in WTFCrashWithInfo(int, char const*, char const*, int) at /Volumes/.../OpenSource/WebKitBuild/Debug/usr/local/include/wtf/Assertions.h:559
#2  0x00000007ab68f043 in WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer*, WebCore::RenderLayer&, WebCore::RenderLayerCompositor::OverlapMap&, WebCore::RenderLayerCompositor::CompositingState&, bool&) at /Volumes/.../OpenSource/Source/WebCore/rendering/RenderLayerCompositor.cpp:983
#3  0x00000007ab68ebab in WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer*, WebCore::RenderLayer&, WebCore::RenderLayerCompositor::OverlapMap&, WebCore::RenderLayerCompositor::CompositingState&, bool&) at /Volumes/.../OpenSource/Source/WebCore/rendering/RenderLayerCompositor.cpp:901
#4  0x00000007ab68ebab in WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer*, WebCore::RenderLayer&, WebCore::RenderLayerCompositor::OverlapMap&, WebCore::RenderLayerCompositor::CompositingState&, bool&) at /Volumes/.../OpenSource/Source/WebCore/rendering/RenderLayerCompositor.cpp:901
#5  0x00000007ab68ebab in WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer*, WebCore::RenderLayer&, WebCore::RenderLayerCompositor::OverlapMap&, WebCore::RenderLayerCompositor::CompositingState&, bool&) at /Volumes/.../OpenSource/Source/WebCore/rendering/RenderLayerCompositor.cpp:901
#6  0x00000007ab68ebab in WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer*, WebCore::RenderLayer&, WebCore::RenderLayerCompositor::OverlapMap&, WebCore::RenderLayerCompositor::CompositingState&, bool&) at /Volumes/.../OpenSource/Source/WebCore/rendering/RenderLayerCompositor.cpp:901
#7  0x00000007ab66037f in WebCore::RenderLayerCompositor::updateCompositingLayers(WebCore::CompositingUpdateType, WebCore::RenderLayer*) at /Volumes/.../OpenSource/Source/WebCore/rendering/RenderLayerCompositor.cpp:729
#8  0x00000007aae2c0b3 in WebCore::FrameView::updateCompositingLayersAfterLayout() at /Volumes/.../OpenSource/Source/WebCore/page/FrameView.cpp:850
#9  0x00000007aae2e967 in WebCore::FrameView::didLayout(WTF::WeakPtr<WebCore::RenderElement>) at /Volumes/.../OpenSource/Source/WebCore/page/FrameView.cpp:1300
#10 0x00000007aae6c9fb in WebCore::FrameViewLayoutContext::layout() at /Volumes/.../OpenSource/Source/WebCore/page/FrameViewLayoutContext.cpp:239
#11 0x00000007aa2f7966 in WebCore::Document::updateLayout() at /Volumes/.../OpenSource/Source/WebCore/dom/Document.cpp:2091
#12 0x00000007aa2f8ede in WebCore::Document::updateLayoutIgnorePendingStylesheets(WebCore::Document::RunPostLayoutTasks) at /Volumes/.../OpenSource/Source/WebCore/dom/Document.cpp:2105
#13 0x00000007a9ce467e in WebCore::AccessibilityObject::updateBackingStore() at /Volumes/.../OpenSource/Source/WebCore/accessibility/AccessibilityObject.cpp:1787
#14 0x00000007abea5b23 in ::-[WebAccessibilityObjectWrapperBase updateObjectBackingStore]() at /Volumes/.../OpenSource/Source/WebCore/accessibility/mac/WebAccessibilityObjectWrapperBase.mm:292
#15 0x00000007abebeb5c in ::-[WebAccessibilityObjectWrapper accessibilityIsIgnored]() at /Volumes/.../OpenSource/Source/WebCore/accessibility/mac/WebAccessibilityObjectWrapperMac.mm:3371
#16 0x00000007a842ee2b in WebCore::AXObjectCache::postPlatformNotification(WebCore::AccessibilityObject*, WebCore::AXObjectCache::AXNotification) at /Volumes/.../OpenSource/Source/WebCore/accessibility/mac/AXObjectCacheMac.mm:350
#17 0x00000007a9c863e1 in WebCore::AXObjectCache::notificationPostTimerFired() at /Volumes/.../OpenSource/Source/WebCore/accessibility/AXObjectCache.cpp:922
#18 0x00000007a9caf101 in decltype(*(std::__1::forward<WebCore::AXObjectCache*&>(fp0)).*fp()) std::__1::__invoke<void (WebCore::AXObjectCache::*&)(), WebCore::AXObjectCache*&, void>(void (WebCore::AXObjectCache::*&)(), WebCore::AXObjectCache*&) at /Volumes/Xcode/Xcode.app/Contents/Developer/Toolchains/OSX10.15.xctoolchain/usr/include/c++/v1/type_traits:4286
#19 0x00000007a9caf060 in std::__1::__bind_return<void (WebCore::AXObjectCache::*)(), std::__1::tuple<WebCore::AXObjectCache*>, std::__1::tuple<>, __is_valid_bind_return<void (WebCore::AXObjectCache::*)(), std::__1::tuple<WebCore::AXObjectCache*>, std::__1::tuple<> >::value>::type std::__1::__apply_functor<void (WebCore::AXObjectCache::*)(), std::__1::tuple<WebCore::AXObjectCache*>, 0ul, std::__1::tuple<> >(void (WebCore::AXObjectCache::*&)(), std::__1::tuple<WebCore::AXObjectCache*>&, std::__1::__tuple_indices<0ul>, std::__1::tuple<>&&) at /Volumes/Xcode/Xcode.app/Contents/Developer/Toolchains/OSX10.15.xctoolchain/usr/include/c++/v1/functional:2216
#20 0x00000007a9caf00c in std::__1::__bind_return<void (WebCore::AXObjectCache::*)(), std::__1::tuple<WebCore::AXObjectCache*>, std::__1::tuple<>, __is_valid_bind_return<void (WebCore::AXObjectCache::*)(), std::__1::tuple<WebCore::AXObjectCache*>, std::__1::tuple<> >::value>::type std::__1::__bind<void (WebCore::AXObjectCache::*&)(), WebCore::AXObjectCache*>::operator()<>() at /Volumes/Xcode/Xcode.app/Contents/Developer/Toolchains/OSX10.15.xctoolchain/usr/include/c++/v1/functional:2249
#21 0x00000007a9caefa9 in WTF::Function<void ()>::CallableWrapper<std::__1::__bind<void (WebCore::AXObjectCache::*&)(), WebCore::AXObjectCache*> >::call() at /Volumes/.../OpenSource/WebKitBuild/Debug/usr/local/include/wtf/Function.h:101
#22 0x00000007a800f4da in WTF::Function<void ()>::operator()() const at /Volumes/.../OpenSource/WebKitBuild/Debug/usr/local/include/wtf/Function.h:56
#23 0x00000007a80aad09 in WebCore::Timer::fired() at /Volumes/.../OpenSource/Source/WebCore/platform/Timer.h:131
#24 0x00000007ab0433d9 in WebCore::ThreadTimers::sharedTimerFiredInternal() at /Volumes/.../OpenSource/Source/WebCore/platform/ThreadTimers.cpp:117
#25 0x00000007ab04dc31 in WebCore::ThreadTimers::setSharedTimer(WebCore::SharedTimer*)::$_0::operator()() const at /Volumes/.../OpenSource/Source/WebCore/platform/ThreadTimers.cpp:69
#26 0x00000007ab04dbe9 in WTF::Function<void ()>::CallableWrapper<WebCore::ThreadTimers::setSharedTimer(WebCore::SharedTimer*)::$_0>::call() at /Volumes/.../OpenSource/WebKitBuild/Debug/usr/local/include/wtf/Function.h:101
#27 0x00000007a800f4da in WTF::Function<void ()>::operator()() const at /Volumes/.../OpenSource/WebKitBuild/Debug/usr/local/include/wtf/Function.h:56
#28 0x00000007ab019e07 in WebCore::MainThreadSharedTimer::fired() at /Volumes/.../OpenSource/Source/WebCore/platform/MainThreadSharedTimer.cpp:83
#29 0x00000007ab0a1916 in WebCore::timerFired(__CFRunLoopTimer*, void*) at /Volumes/.../OpenSource/Source/WebCore/platform/cf/MainThreadSharedTimerCF.cpp:74

[Daniel Bates]

Here is some output from lldb:

(lldb) p queryData
(WebCore::RenderLayerCompositor::RequiresCompositingData) $0 = {
  layoutUpToDate = Yes
  nonCompositedForPositionReason = NoNotCompositedReason
  reevaluateAfterLayout = false
}
(lldb) p layer
(WebCore::RenderLayer) $5 = {
  WebCore::ScrollableArea = {
    WTF::CanMakeWeakPtr<WebCore::ScrollableArea> = {
      m_weakFactory = {
        m_ref = {
          m_ptr = 0x0000000000000000
        }
      }
    }
    m_scrollAnimator = {
      __ptr_ = {
        std::__1::__compressed_pair_elem<WebCore::ScrollAnimator *, 0, false> = {
          __value_ = 0x0000000000000000
        }
      }
    }
    m_snapOffsetsInfo = {
      __ptr_ = {
        std::__1::__compressed_pair_elem<WebCore::ScrollSnapOffsetsInfo<WebCore::LayoutUnit> *, 0, false> = {
          __value_ = 0x0000000000000000
        }
      }
    }
    m_currentHorizontalSnapPointIndex = 0
    m_currentVerticalSnapPointIndex = 0
    m_scrollOrigin = { x = 0, y = 0 }
    m_constrainsScrollingToContentEdge = 1
    m_inLiveResize = 0
    m_verticalScrollElasticity = 1
    m_horizontalScrollElasticity = 1
    m_scrollbarOverlayStyle = 0
    m_scrollOriginChanged = 0
    m_scrolledProgrammatically = 0
  }
  m_compositingDirtyBits = { size = 4 } {
    HasDescendantNeedingRequirementsTraversal = 1
    HasDescendantNeedingBackingOrHierarchyTraversal = 2
    NeedsGeometryUpdate = 64
    NeedsConfigurationUpdate = 128
  }
  m_isRenderViewLayer = false
  m_forcedStackingContext = false
  m_isNormalFlowOnly = false
  m_isStackingContext = true
  m_zOrderListsDirty = false
  m_normalFlowListDirty = false
  m_hadNegativeZOrderList = false
  m_inResizeMode = false
  m_scrollDimensionsDirty = false
  m_isSelfPaintingLayer = true
  m_hasSelfPaintingLayerDescendant = true
  m_hasSelfPaintingLayerDescendantDirty = false
  m_usedTransparency = false
  m_paintingInsideReflection = false
  m_inOverflowRelayout = false
  m_repaintStatus = 0
  m_visibleContentStatusDirty = false
  m_hasVisibleContent = true
  m_visibleDescendantStatusDirty = false
  m_hasVisibleDescendant = true
  m_registeredScrollableArea = false
  m_isFixedIntersectingViewport = false
  m_3DTransformedDescendantStatusDirty = false
  m_has3DTransformedDescendant = false
  m_hasCompositingDescendant = false
  m_hasTransformedAncestor = true
  m_has3DTransformedAncestor = false
  m_indirectCompositingReason = 0
  m_viewportConstrainedNotCompositedReason = 0
  m_containsDirtyOverlayScrollbars = false
  m_updatingMarqueePosition = false
  m_layerListMutationAllowed = false
  m_blendMode = 1
  m_hasNotIsolatedCompositedBlendingDescendants = false
  m_hasNotIsolatedBlendingDescendants = false
  m_hasNotIsolatedBlendingDescendantsStatusDirty = false
  m_renderer = 0x00000007db100ea0
  m_parent = 0x00000007d8e2b2a0
  m_previous = 0x0000000000000000
  m_next = 0x00000007d8e2b7e0
  m_first = 0x00000007d8e2b540
  m_last = 0x00000007d8e2b540
  m_posZOrderList = {
    __ptr_ = {
      std::__1::__compressed_pair_elem<WTF::Vector<WebCore::RenderLayer *, 0, WTF::CrashOnOverflow, 16> *, 0, false> = {
        __value_ = 0x00000007d8e05ab0 { size = 1, capacity = 16 }
      }
    }
  }
  m_negZOrderList = {
    __ptr_ = {
      std::__1::__compressed_pair_elem<WTF::Vector<WebCore::RenderLayer *, 0, WTF::CrashOnOverflow, 16> *, 0, false> = {
        __value_ = 0x0000000000000000 { size = 0, capacity = 0 }
      }
    }
  }
  m_normalFlowList = {
    __ptr_ = {
      std::__1::__compressed_pair_elem<WTF::Vector<WebCore::RenderLayer *, 0, WTF::CrashOnOverflow, 16> *, 0, false> = {
        __value_ = 0x0000000000000000 { size = 0, capacity = 0 }
      }
    }
  }
  m_offsetForInFlowPosition = { width = 0px (0), height = 0px (0) }
  m_topLeft = { x = 0px (0), y = 0px (0) }
  m_layerSize = { width = 249, height = 187 }
  m_scrollPosition = { x = 0, y = 0 }
  m_postLayoutScrollPosition = {
    WTF::OptionalBase<WebCore::IntPoint> = {
      init_ = false
      storage_ = (dummy_ = '\0', value_ = { x = 0, y = 0 })
    }
  }
  m_scrollSize = { width = 249, height = 187 }
  m_hBar = {
    m_ptr = 0x0000000000000000
  }
  m_vBar = {
    m_ptr = 0x0000000000000000
  }
  m_clipRectsCache = {
    __ptr_ = {
      std::__1::__compressed_pair_elem<WebCore::ClipRectsCache *, 0, false> = {
        __value_ = 0x0000001c0023d1b8
      }
    }
  }
  m_cachedOverlayScrollbarOffset = { x = 0, y = 0 }
  m_marquee = {
    __ptr_ = {
      std::__1::__compressed_pair_elem<WebCore::RenderMarquee *, 0, false> = {
        __value_ = 0x0000000000000000
      }
    }
  }
  m_staticInlinePosition = { 0px (0) }
  m_staticBlockPosition = { 0px (0) }
  m_transform = {
    __ptr_ = {
      std::__1::__compressed_pair_elem<WebCore::TransformationMatrix *, 0, false> = {
        __value_ = 0x0000000000000000
      }
    }
  }
  m_reflection = {
    __ptr_ = {
      std::__1::__compressed_pair_elem<WebCore::RenderReplica *, 0, false> = {
        __value_ = 0x0000000000000000
      }
    }
  }
  m_scrollCorner = {
    __ptr_ = {
      std::__1::__compressed_pair_elem<WebCore::RenderScrollbarPart *, 0, false> = {
        __value_ = 0x0000000000000000
      }
    }
  }
  m_resizer = {
    __ptr_ = {
      std::__1::__compressed_pair_elem<WebCore::RenderScrollbarPart *, 0, false> = {
        __value_ = 0x0000000000000000
      }
    }
  }
  m_enclosingPaginationLayer = {
    m_ref = {
      m_ptr = 0x0000000000000000
    }
  }
  m_blockSelectionGapsBounds = { x = 0, y = 0, width = 0, height = 0 }
  m_filters = {
    __ptr_ = {
      std::__1::__compressed_pair_elem<WebCore::RenderLayerFilters *, 0, false> = {
        __value_ = 0x0000000000000000
      }
    }
  }
  m_backing = {
    __ptr_ = {
      std::__1::__compressed_pair_elem<WebCore::RenderLayerBacking *, 0, false> = {
        __value_ = 0x0000001c01a5c398
      }
    }
  }
  m_paintFrequencyTracker = {
    m_firstPaintTime = (m_value = 170826.30389103701)
    m_lastPaintTime = (m_value = 170826.991178608)
    m_totalPaints = 3
    m_paintFrequency = Low
  }
}
(lldb) p willBeComposited
(bool) $10 = true
(lldb) p canBeComposited(layer)
(bool) $11 = true
(lldb) p requiresCompositingLayer(layer, queryData)
(bool) $12 = false
(lldb) p layer.mustCompositeForIndirectReasons()
(bool) $13 = false
(lldb) p usesCompositing() && layer.isRenderViewLayer()
(bool) $14 = false

[Daniel Bates]

Because of the following:

> (lldb) p canBeComposited(layer)
> (bool) $11 = true
> (lldb) p requiresCompositingLayer(layer, queryData)
> (bool) $12 = false
> (lldb) p layer.mustCompositeForIndirectReasons()
> (bool) $13 = false
> (lldb) p usesCompositing() && layer.isRenderViewLayer()
> (bool) $14 = false

RenderLayerCompositor::needsToBeComposited() returns false.