thread 'StyleThread#2' panicked at 'already mutably borrowed', /home/worker/workspace/build/src/third_party/rust/atomic_refcell/src/lib.rs:161
stack backtrace:
   0:     0x7f6f99931ac3 - std::sys::imp::backtrace::tracing::imp::unwind_backtrace::hcab99e0793da62c7
                               at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1:     0x7f6f9992ea89 - std::panicking::default_hook::{{closure}}::h9ba2c6973907a2be
                               at /checkout/src/libstd/sys_common/backtrace.rs:71
                               at /checkout/src/libstd/sys_common/backtrace.rs:60
                               at /checkout/src/libstd/panicking.rs:355
   2:     0x7f6f9992deb0 - std::panicking::default_hook::he4d55e2dd21c3cca
                               at /checkout/src/libstd/panicking.rs:371
   3:     0x7f6f9992d9d5 - std::panicking::rust_panic_with_hook::ha138c05cd33ad44d
                               at /checkout/src/libstd/panicking.rs:549
   4:     0x7f6f998b00ef - std::panicking::begin_panic::h4d68aac0b79bfb98
                               at /checkout/src/libstd/panicking.rs:511
   5:     0x7f6f998b00a5 - atomic_refcell::AtomicBorrowRef::do_panic::hbcc7af3a774ab2dd
                               at /home/worker/workspace/build/src/third_party/rust/atomic_refcell/src/lib.rs:161
   6:     0x7f6f99651b83 - <style::values::specified::color::Color as style::values::computed::ToComputedValue>::to_computed_value::h43831540927a6f94
