Intermittent crash in upgrade-protocol.keep-origin-redirect.http.html

[upsuper]

 ▶ CRASH [expected TIMEOUT] /referrer-policy/strict-origin/meta-referrer/cross-origin/http-https/iframe-tag/upgrade-protocol.keep-origin-redirect.http.html
  │ 
  │ VMware, Inc.
  │ softpipe
  │ 3.3 (Core Profile) Mesa 17.3.0-devel
  │ failed to receive response to font request: Io(Os { code: 104, kind: ConnectionReset, message: "Connection reset by peer" }) (thread LayoutThread PipelineId { namespace_id: PipelineNamespaceId(0), index: PipelineIndex(NonZero(NonZero(1))) }, at libcore/result.rs:916)
  │ stack backtrace:
  │    0:     0x7f93c2317b6c - backtrace::backtrace::trace::hb73e73c3fa21d7b2
  │    1:     0x7f93c2316d12 - backtrace::capture::Backtrace::new::h8a585c120187c23d
  │    2:     0x7f93bfa4ebdf - servo::main::{{closure}}::h0e156dceb3a3caca
  │    3:     0x7f93c23256a5 - std::panicking::rust_panic_with_hook::haa00f5a9417cd684
  │                         at libstd/panicking.rs:577
  │    4:     0x7f93c232552e - std::panicking::begin_panic::ha956683198499384
  │                         at libstd/panicking.rs:537
  │    5:     0x7f93c232542a - std::panicking::begin_panic_fmt::h587e116719f14631
  │                         at libstd/panicking.rs:521
  │    6:     0x7f93c23253c2 - rust_begin_unwind
  │                         at libstd/panicking.rs:497
  │    7:     0x7f93c2359c50 - core::panicking::panic_fmt::h1d64949939b0af2f
  │                         at libcore/panicking.rs:71
  │    8:     0x7f93c0fd7c0d - core::result::unwrap_failed::hb8a3a2c98e7238cc
  │    9:     0x7f93c0fd4b80 - gfx::font_cache_thread::FontCacheThread::get_font_instance::h7f5e67456bb670f9
  │   10:     0x7f93c0fd4e89 - gfx::font_context::FontContext::create_layout_font::hc243a4ae254135a4
  │   11:     0x7f93c0fd569b - gfx::font_context::FontContext::layout_font_group_for_style::h9b03c34e1d0d2a4c
  │   12:     0x7f93c0d518f0 - layout::inline::InlineFlow::minimum_line_metrics_for_fragments::h2d24db603d547744
  │   13:     0x7f93bfc5a980 - <std::thread::local::LocalKey<T>>::with::h3c7624111148fa9e
  │   14:     0x7f93bfd96e9d - <layout::construct::FlowConstructor<'a, ConcreteThreadSafeLayoutNode>>::build_flow_for_block_starting_with_fragments::h3717dbffb126350a
  │   15:     0x7f93bfd9482a - <layout::construct::FlowConstructor<'a, ConcreteThreadSafeLayoutNode>>::build_flow_for_block_like::h87affd50647c8e27
  │   16:     0x7f93bfd93fc7 - <layout::construct::FlowConstructor<'a, ConcreteThreadSafeLayoutNode>>::build_flow_for_block::h17f71da37e534197
  │   17:     0x7f93bfd7f942 - <layout::construct::FlowConstructor<'a, ConcreteThreadSafeLayoutNode> as layout::traversal::PostorderNodeMutTraversal<ConcreteThreadSafeLayoutNode>>::process::hc79f5142fc29eae9
  │   18:     0x7f93bfd7a079 - style::traversal::DomTraversal::handle_postorder_traversal::h6f8f3138f3255e65
  │   19:     0x7f93bfcaab5f - style::driver::traverse_dom::h9b6aea88f97a26a5
  │   20:     0x7f93bfc894a7 - layout_thread::LayoutThread::handle_reflow::hc4b1116499236010
  │   21:     0x7f93bfc835dc - layout_thread::LayoutThread::handle_request_helper::ha4b7265fc9e60f92
  │   22:     0x7f93bfc81fd9 - layout_thread::LayoutThread::start::h40fe2396bed94368
  │   23:     0x7f93bfd6a143 - profile_traits::mem::ProfilerChan::run_with_memory_reporting::h28a011942351d0c7
  │   24:     0x7f93bfc9c0cb - std::sys_common::backtrace::__rust_begin_short_backtrace::hedb9aad1571236b4
  │   25:     0x7f93bfc568a7 - _ZN3std9panicking3try7do_call17haa6c476007cbe30cE.llvm.5EBEDCF9
  │   26:     0x7f93c234e49e - __rust_maybe_catch_panic
  │                         at libpanic_unwind/lib.rs:102
  │   27:     0x7f93bfcd41aa - <F as alloc::boxed::FnBox<A>>::call_box::hf33d8def7d226953
  │   28:     0x7f93c23391eb - <alloc::boxed::Box<alloc::boxed::FnBox<A, Output$u3d$R$GT$$u20$$u2b$$u20$$u27$a$GT$$u20$as$u20$core..ops..function..FnOnce$LT$A$GT$$GT$::call_once::h13f1b0bf377a9f5b
  │                         at /checkout/src/liballoc/boxed.rs:798
  │                          - std::sys_common::thread::start_thread::hb5b6e0447b9691dc
  │                         at libstd/sys_common/thread.rs:24
  │                          - std::sys::unix::thread::Thread::new::thread_start::hcaff0bef1a01c624
  │                         at libstd/sys/unix/thread.rs:90
  │   29:     0x7f93be934183 - start_thread
  │   30:     0x7f93bd1fc03c - clone
  │   31:                0x0 - <unknown>
  │ ERROR:servo: failed to receive response to font request: Io(Os { code: 104, kind: ConnectionReset, message: "Connection reset by peer" })
  │ Pipeline failed in hard-fail mode.  Crashing!
  └ thread panicked while processing panic. aborting.

[jdm]

This is #19033.