Intermittent CRASH in /referrer-policy/gen/req.attr/no-referrer-when-downgrade/a-tag/cross-https.no-redirect.http.html

[gterzian]

https://community-tc.services.mozilla.com/tasks/V-7BZUHJTS6oQvd-JpUUCg

No URL for Core Text font! (thread FontCacheThread, at src/libcore/option.rs:1188)
  │ stack backtrace:
  │    0: <servo::backtrace::Print as core::fmt::Debug>::fmt
  │    1: core::fmt::write
  │    2: <std::io::stdio::Stdout as std::io::Write>::write_fmt
  │    3: std::io::stdio::_print
  │    4: servo::backtrace::print
  │    5: servo::main::{{closure}}
  │    6: std::panicking::rust_panic_with_hook
  │    7: rust_begin_unwind
  │    8: core::panicking::panic_fmt
  │    9: core::option::expect_failed
  │   10: gfx::platform::macos::font_template::FontTemplateData::bytes
  │   11: gfx::font_cache_thread::FontCache::run
  │   12: std::sys_common::backtrace::__rust_begin_short_backtrace
  │   13: _ZN3std9panicking3try7do_call17ha825f387d775fdf6E.llvm.4064580437743660061
  │   14: __rust_maybe_catch_panic
  │   15: core::ops::function::FnOnce::call_once{{vtable.shim}}
  │   16: <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once
  │   17: std::sys::unix::thread::Thread::new::thread_start
  │   18: _pthread_body
  │   19: _pthread_start

Font cache thread has already exited. (thread LayoutThread PipelineId { namespace_id: PipelineNamespaceId(1), index: PipelineIndex(1) }, at components/gfx/font_cache_thread.rs:547)
  │ stack backtrace:
  │    0: <servo::backtrace::Print as core::fmt::Debug>::fmt
  │    1: core::fmt::write
  │    2: <std::io::stdio::Stdout as std::io::Write>::write_fmt
  │    3: std::io::stdio::_print
  │    4: servo::backtrace::print
  │    5: servo::main::{{closure}}
  │    6: std::panicking::rust_panic_with_hook
  │    7: std::panicking::begin_panic
  │    8: <gfx::font_cache_thread::FontCacheThread as gfx::font_context::FontSource>::font_template
  │    9: gfx::font_context::FontContext<S>::font
  │   10: gfx::font::FontGroup::first
  │   11: layout::text::font_metrics_for_style
  │   12: layout::inline::InlineFlow::minimum_line_metrics_for_fragments
  │   13: std::thread::local::LocalKey<T>::with
  │   14: layout::construct::FlowConstructor<ConcreteThreadSafeLayoutNode>::build_flow_for_block_starting_with_fragments
  │   15: layout::construct::FlowConstructor<ConcreteThreadSafeLayoutNode>::build_flow_for_block_like
  │   16: layout::construct::FlowConstructor<ConcreteThreadSafeLayoutNode>::build_flow_for_block
  │   17: <layout::construct::FlowConstructor<ConcreteThreadSafeLayoutNode> as layout::traversal::PostorderNodeMutTraversal<ConcreteThreadSafeLayoutNode>>::process
  │   18: style::traversal::DomTraversal::handle_postorder_traversal
  │   19: style::driver::traverse_dom
  │   20: profile_traits::time::profile
  │   21: layout_thread::LayoutThread::handle_reflow
  │   22: profile_traits::time::profile
  │   23: layout_thread::LayoutThread::handle_request_helper
  │   24: layout_thread::LayoutThread::start
  │   25: profile_traits::mem::ProfilerChan::run_with_memory_reporting
  │   26: std::sys_common::backtrace::__rust_begin_short_backtrace
│   27: _ZN3std9panicking3try7do_call17hc35ccd84c765f464E.llvm.16407149628361202227
  │   28: __rust_maybe_catch_panic
  │   29: core::ops::function::FnOnce::call_once{{vtable.shim}}
  │   30: <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once
  │   31: std::sys::unix::thread::Thread::new::thread_start
  │   32: _pthread_body
  │   33: _pthread_start
  │ 
  │ [2020-01-12T06:45:39Z ERROR servo] Font cache thread has already exited.
  │ Pipeline failed in hard-fail mode.  Crashing!
  │ thread panicked while processing panic. aborting.
  └ thread panicked while processing panic. aborting.

[gterzian]

Related, or perhaps duplicate, of #24622 #24369

[jdm]

#24622