▶ TIMEOUT [expected PASS] /_mozilla/css/iframe/hide_layers2.html
  │ 
  │ thread 'Constellation' panicked at 'unable to find pipeline - this is a bug', ../src/libcore/option.rs:335
  │ stack backtrace:
  │    1:        0x10d215d08 - sys::backtrace::tracing::imp::write::h3ed615ef3cda9b6b7It
  │    2:        0x10d217e4f - panicking::log_panic::_<closure>::closure.40650
  │    3:        0x10d2178f2 - panicking::log_panic::hdfd4a4ec7b55d6a5MAx
  │    4:        0x10d202de6 - sys_common::unwind::begin_unwind_inner::h2f70decd24e7a2917Ls
  │    5:        0x10d2031ce - sys_common::unwind::begin_unwind_fmt::h29da0d611b24747ddLs
  │    6:        0x10d215327 - rust_begin_unwind
  │    7:        0x10d23a430 - panicking::panic_fmt::h2f3428e3725b99d6VFK
  │    8:        0x10bc3e62d - constellation::_<impl>::handle_request::handle_request::h17802158443733694633
  │    9:        0x10bc23aa7 - sys_common::unwind::try::try_fn::try_fn::h5102255439231410249
  │   10:        0x10d215148 - __rust_try
  │   11:        0x10d21224e - sys_common::unwind::try::inner_try::hd7e4f8fc422767d2FIs
  │   12:        0x10bc25b6a - boxed::_<impl>::call_box::call_box::h3181868436741623310
  │   13:        0x10d2170dd - sys::thread::_<impl>::new::thread_start::ha2c46efb1706c462jVw
  │   14:     0x7fff91449059 - _pthread_body
  └   15:     0x7fff91448fd6 - _pthread_start