Stable unexpected results (1): 
  ▶ CRASH [expected OK] /intersection-observer/nested-cross-origin-iframe.sub.html
  │ 
  │ Should always have a StackingContextTree for geometry queries (thread Script(2,3), at components/layout/layout_impl.rs:268)
  │    0: servoshell::backtrace::print
  │    1: servoshell::panic_hook::panic_hook
  │    2: std::panicking::rust_panic_with_hook
  │    3: std::panicking::begin_panic_handler::{{closure}}
  │    4: std::sys::backtrace::__rust_end_short_backtrace
  │    5: rust_begin_unwind
  │    6: core::panicking::panic_fmt
  │    7: core::option::expect_failed
  │    8: <layout::layout_impl::LayoutThread as layout_api::Layout>::query_content_box
  │    9: script::dom::node::Node::bounding_content_box_no_reflow
  │   10: script::dom::intersectionobserver::IntersectionObserver::update_intersection_observations_steps
  │   11: script::dom::document::Document::update_intersection_observer_steps
  │   12: script::script_thread::ScriptThread::update_the_rendering
  │   13: script::script_thread::ScriptThread::start
  │   14: profile_traits::mem::ProfilerChan::run_with_memory_reporting
  │   15: std::sys::backtrace::__rust_begin_short_backtrace
  │   16: core::ops::function::FnOnce::call_once{{vtable.shim}}
  │   17: std::sys::pal::unix::thread::Thread::new::thread_start
  │   18: <unknown>
  └   19: <unknown>