Assertion failure: owned->SafeElementAt(idx) != child (Already in place!), at /src/accessible/generic/DocAccessible.cpp:2152 #0 mozilla::a11y::DocAccessible::DoARIAOwnsRelocation(mozilla::a11y::Accessible*) /src/accessible/generic/DocAccessible.cpp:2095:15 #1 mozilla::a11y::NotificationController::WillRefresh(mozilla::TimeStamp) /src/accessible/base/NotificationController.cpp:818:18 #2 nsRefreshDriver::Tick(long, mozilla::TimeStamp) /src/layout/base/nsRefreshDriver.cpp:1843:12 #3 mozilla::RefreshDriverTimer::TickRefreshDrivers(long, mozilla::TimeStamp, nsTArray<RefPtr<nsRefreshDriver> >&) /src/layout/base/nsRefreshDriver.cpp:306:7 #4 mozilla::RefreshDriverTimer::Tick(long, mozilla::TimeStamp) /src/layout/base/nsRefreshDriver.cpp:328:5 #5 mozilla::VsyncRefreshDriverTimer::RunRefreshDrivers(mozilla::TimeStamp) /src/layout/base/nsRefreshDriver.cpp:769:5 #6 mozilla::VsyncRefreshDriverTimer::RefreshDriverVsyncObserver::TickRefreshDriver(mozilla::TimeStamp) /src/layout/base/nsRefreshDriver.cpp:682:35 #7 mozilla::VsyncRefreshDriverTimer::RefreshDriverVsyncObserver::NotifyVsync(mozilla::TimeStamp) /src/layout/base/nsRefreshDriver.cpp:583:9 #8 mozilla::layout::VsyncChild::RecvNotify(mozilla::TimeStamp const&) /src/layout/ipc/VsyncChild.cpp:68:16 #9 mozilla::layout::PVsyncChild::OnMessageReceived(IPC::Message const&) /src/obj-firefox/ipc/ipdl/PVsyncChild.cpp:155:20 #10 mozilla::ipc::PBackgroundChild::OnMessageReceived(IPC::Message const&) /src/obj-firefox/ipc/ipdl/PBackgroundChild.cpp:1812:28 #11 mozilla::ipc::MessageChannel::DispatchAsyncMessage(IPC::Message const&) /src/ipc/glue/MessageChannel.cpp:2110:25 #12 mozilla::ipc::MessageChannel::DispatchMessage(IPC::Message&&) /src/ipc/glue/MessageChannel.cpp:2040:17 #13 mozilla::ipc::MessageChannel::RunMessage(mozilla::ipc::MessageChannel::MessageTask&) /src/ipc/glue/MessageChannel.cpp:1886:5 #14 mozilla::ipc::MessageChannel::MessageTask::Run() /src/ipc/glue/MessageChannel.cpp:1919:15 #15 nsThread::ProcessNextEvent(bool, bool*) /src/xpcom/threads/nsThread.cpp:1033:14 #16 NS_ProcessNextEvent(nsIThread*, bool) /src/xpcom/threads/nsThreadUtils.cpp:508:10 #17 mozilla::ipc::MessagePump::Run(base::MessagePump::Delegate*) /src/ipc/glue/MessagePump.cpp:125:5 #18 MessageLoop::RunInternal() /src/ipc/chromium/src/base/message_loop.cc:326:10 #19 MessageLoop::Run() /src/ipc/chromium/src/base/message_loop.cc:299:3 #20 nsBaseAppShell::Run() /src/widget/nsBaseAppShell.cpp:157:27 #21 XRE_RunAppShell() /src/toolkit/xre/nsEmbedFunctions.cpp:865:22 #22 mozilla::ipc::MessagePumpForChildProcess::Run(base::MessagePump::Delegate*) /src/ipc/glue/MessagePump.cpp:269:9 #23 MessageLoop::RunInternal() /src/ipc/chromium/src/base/message_loop.cc:326:10 #24 MessageLoop::Run() /src/ipc/chromium/src/base/message_loop.cc:299:3 #25 XRE_InitChildProcess(int, char**, XREChildData const*) /src/toolkit/xre/nsEmbedFunctions.cpp:691:34 #26 content_process_main(mozilla::Bootstrap*, int, char**) /src/browser/app/../../ipc/contentproc/plugin-container.cpp:63:30 #27 main /src/browser/app/nsBrowserApp.cpp:280:18 #28 __libc_start_main /build/glibc-bfm8X4/glibc-2.23/csu/../csu/libc-start.c:291 #29 _start (/home/user/workspace/browsers/m-c-1512418880-asan-debug/firefox+0x41f114)

Looks like my patch in bug 1405796 will fix this. We'll wait to that lands for you to confirm.