Intermittent crash in /custom-elements/throw-on-dynamic-markup-insertion-counter-construct.html, /custom-elements/throw-on-dynamic-markup-insertion-counter-reactions.html

[jdm]

  ▶ CRASH [expected OK] /custom-elements/throw-on-dynamic-markup-insertion-counter-construct.html
  │ 
  │ VMware, Inc.
  │ softpipe
  │ 3.3 (Core Profile) Mesa 18.3.0-devel
  │ called `Result::unwrap()` on an `Err` value: "SendError(..)" (thread ScriptThread PipelineId { namespace_id: PipelineNamespaceId(1), index: PipelineIndex(1) }, at libcore/result.rs:1009)
  │ 2018-12-11 20:51:06.671 servo[13335:313581513] Metadata.framework [Error]: couldn't get the client port
  │ stack backtrace:
  │    0:        0x109f8c32e - __ZN9backtrace9backtrace5trace17hfb299a80de9f2c59E
  │    1:        0x109f8d03c - __ZN72_$LT$backtrace..capture..Backtrace$u20$as$u20$core..default..Default$GT$7default17hc2efebe8cdde4f0dE
  │    2:        0x109f8d0bd - __ZN9backtrace7capture9Backtrace3new17hda81718f1b689ebbE
  │    3:        0x107b48572 - __ZN5servo4main28_$u7b$$u7b$closure$u7d$$u7d$17h0d76177a805c671dE
  │    4:        0x10a9e5b18 - __ZN3std9panicking20rust_panic_with_hook17h14490a1041ee4235E
  │    5:        0x10a9e562c - __ZN3std9panicking18continue_panic_fmt17h7beddad0ba45f4eaE
  │    6:        0x10a9e5518 - _rust_begin_unwind
  │    7:        0x10aa02e81 - __ZN4core9panicking9panic_fmt17hc2d37e7312d32a42E
  │    8:        0x108731bfd - __ZN4core6result13unwrap_failed17h6b97f30c26b7d48dE
  │    9:        0x1083c4ad6 - __ZN6script3dom6window6Window12force_reflow17h3fef6e349bdc64d8E
  │   10:        0x1083c50dd - __ZN6script3dom6window6Window6reflow17h7c1be57680844861E
  │   11:        0x108632e01 - __ZN6script3dom8document8Document11finish_load17h003bc1cbf07c56a0E
  │   12:        0x1085a5186 - __ZN6script3dom11servoparser11ServoParser13do_parse_sync17h5b5caa75a0ab3048E
  │   13:        0x1088454bc - __ZN14profile_traits4time7profile17hdbf206f3ae62587cE
  │   14:        0x1085a4b43 - __ZN6script3dom11servoparser11ServoParser10parse_sync17h31c8845458b23bf3E.llvm.15728927234061289882
  │   15:        0x1085a8d74 - __ZN93_$LT$script..dom..servoparser..ParserContext$u20$as$u20$net_traits..FetchResponseListener$GT$20process_response_eof17hfbe6b95c56a88858E
  │   16:        0x1087e92e6 - __ZN6script13script_thread12ScriptThread29handle_msg_from_constellation17hf8f4916ae498a43eE
  │   17:        0x1087e191d - __ZN6script13script_thread12ScriptThread11handle_msgs17he5b44dfb16202a29E.llvm.10621240423632243656
  │   18:        0x108843237 - __ZN14profile_traits3mem12ProfilerChan25run_with_memory_reporting17h0e03acbfc4d99592E
  │   19:        0x10898c06a - __ZN3std10sys_common9backtrace28__rust_begin_short_backtrace17ha40c57d1f4367443E
  │   20:        0x10808a41d - __ZN3std9panicking3try7do_call17hba0d4c902c49a539E.llvm.5047223351545039701
  │   21:        0x10a9f208e - ___rust_maybe_catch_panic
  │   22:        0x108c59af6 - __ZN50_$LT$F$u20$as$u20$alloc..boxed..FnBox$LT$A$GT$$GT$8call_box17h7de07199992c1625E
  │   23:        0x10a9c921b - __ZN3std3sys4unix6thread6Thread3new12thread_start17hba53abd905cebc29E
  │   24:     0x7fffa187799c - __pthread_body
  │   25:     0x7fffa1877919 - __pthread_start
  │ [2018-12-12T01:51:06Z ERROR servo] called `Result::unwrap()` on an `Err` value: "SendError(..)"
  └ Pipeline failed in hard-fail mode.  Crashing!

This looks like it's failing to send a message to the layout thread, which seems surprising.

[pshaughn]

Timeout when I run --headless, crash when I run with a window. (I'm aware sometimes crashes get misreported as timeouts so this might not be a real data point.)