Windowproxy values for discarded browsing contexts can trigger panics

[jdm]

This is the source of the crash in tests/wpt/web-platform-tests/html/browsers/the-window-object/self-et-al.window.js:

pid:73015 called `Option::unwrap()` on a `None` value (thread ScriptThread PipelineId { namespace_id: PipelineNamespaceId(1), index: PipelineIndex(1) }, at src/libcore/option.rs:378)
 0:09.83 pid:73015 stack backtrace:
 0:09.83 pid:73015    0: backtrace::backtrace::libunwind::trace::h654e25ba145ed216 (0x1106070bd)
 0:09.83 pid:73015              at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.35/src/backtrace/libunwind.rs:88
 0:09.83 pid:73015       backtrace::backtrace::trace_unsynchronized::h4e8fe4b833579bb3
 0:09.83 pid:73015              at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.35/src/backtrace/mod.rs:66
 0:09.83 pid:73015    1: backtrace::backtrace::trace::hf75dd54c3b61daf9 (0x110607043)
 0:09.83 pid:73015              at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.35/src/backtrace/mod.rs:53
 0:09.83 pid:73015    2: backtrace::capture::Backtrace::create::h3dc0cdea3cc39d73 (0x1105f5f17)
 0:09.83 pid:73015              at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.35/src/capture.rs:163
 0:09.83 pid:73015    3: backtrace::capture::Backtrace::new::h2429ec5d702fcf24 (0x1105f5e56)
 0:09.83 pid:73015              at /Users/jdm/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.35/src/capture.rs:127
 0:09.83 pid:73015    4: servo::main::{{closure}}::h1d02b72a39d78dcc (0x108ab2212)
 0:09.83 pid:73015              at ports/glutin/main2.rs:116
 0:09.83 pid:73015    5: std::panicking::rust_panic_with_hook::he9c773346a268707 (0x110e32132)
 0:09.83 pid:73015              at src/libstd/panicking.rs:477
 0:09.83 pid:73015    6: std::panicking::continue_panic_fmt::h6ce88923515447fe (0x110e31bcd)
 0:09.84 pid:73015              at src/libstd/panicking.rs:380
 0:09.84 pid:73015    7: rust_begin_unwind (0x110e31b29)
 0:09.84 pid:73015              at src/libstd/panicking.rs:307
 0:09.84 pid:73015    8: std::panicking::begin_panic::h992ed5a1a140acf3 (0x110e9903f)
 0:09.84 pid:73015    9: std::panicking::begin_panic::h992ed5a1a140acf3 (0x110e98f84)
 0:09.84 pid:73015   10: core::option::Option<T>::unwrap::h9b54db8af71f6391 (0x10bd7e35c)
 0:09.84 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libcore/macros.rs:12
 0:09.84 pid:73015   11: script::dom::window::Window::window_proxy::h3e9fe4132ae1d647 (0x10b5cf183)
 0:09.84 pid:73015              at components/script/dom/window.rs:417
 0:09.84 pid:73015   12: <script::dom::window::Window as script::dom::bindings::codegen::Bindings::WindowBinding::WindowBinding::WindowMethods>::Frames::h318dc63e53c0cb43 (0x10b5d26e5)
 0:09.84 pid:73015              at components/script/dom/window.rs:898
 0:09.84 pid:73015   13: script::dom::bindings::codegen::Bindings::WindowBinding::WindowBinding::get_frames::{{closure}}::h943210a0f2805a0c (0x10c25c8a3)
 0:09.84 pid:73015              at /Users/jdm/src/master-servo/target/debug/build/script-decac3ca7e8f26ff/out/Bindings/WindowBinding.rs:1307
 0:09.84 pid:73015   14: core::ops::function::FnOnce::call_once::h48b1b1d5732fb849 (0x10b08e7ad)
 0:09.84 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libcore/ops/function.rs:227
 0:09.84 pid:73015   15: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::h3e8f9fe7ed67e6bb (0x10bf8a298)
 0:09.84 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libstd/panic.rs:315
 0:09.84 pid:73015   16: std::panicking::try::do_call::hbc9be00a0949a103 (0x109c05d1d)
 0:09.84 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libstd/panicking.rs:292
 0:09.84 pid:73015   17: __rust_maybe_catch_panic (0x110e3a39f)
 0:09.84 pid:73015              at src/libpanic_unwind/lib.rs:80
 0:09.84 pid:73015   18: std::panicking::try::heda6978be3e4ada7 (0x109b712f3)
 0:09.84 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libstd/panicking.rs:271
 0:09.84 pid:73015   19: std::panic::catch_unwind::h95c2475b27eb9375 (0x10c0259bf)
 0:09.84 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libstd/panic.rs:394
 0:09.84 pid:73015   20: mozjs::panic::wrap_panic::he446e105d6eeb0bc (0x10aca7af7)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/rust-mozjs-8611526964119dd6/2ef1de9/src/panic.rs:22
 0:09.84 pid:73015   21: script::dom::bindings::codegen::Bindings::WindowBinding::WindowBinding::get_frames::h7b2c40782d55554f (0x10c25c86d)
 0:09.84 pid:73015              at /Users/jdm/src/master-servo/target/debug/build/script-decac3ca7e8f26ff/out/Bindings/WindowBinding.rs:1305
 0:09.84 pid:73015   22: CallJitGetterOp (0x10c83fa3d)
 0:09.84 pid:73015              at src/jsglue.cpp:561
 0:09.84 pid:73015   23: script::dom::bindings::utils::generic_call::h5ca72beb0dda81dd (0x10a95c43a)
 0:09.84 pid:73015              at components/script/dom/bindings/utils.rs:485
 0:09.84 pid:73015   24: script::dom::bindings::utils::generic_getter::h386fc2911e066634 (0x10a95c55c)
 0:09.84 pid:73015              at components/script/dom/bindings/utils.rs:510
 0:09.84 pid:73015   25: _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructE (0x10c871527)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:442
 0:09.84 pid:73015   26: _ZN2js10CallGetterEP9JSContextN2JS6HandleINS2_5ValueEEES5_NS2_13MutableHandleIS4_EE (0x10c872421)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:589
 0:09.84 pid:73015   27: _ZN2js17NativeGetPropertyEP9JSContextN2JS6HandleIPNS_12NativeObjectEEENS3_INS2_5ValueEEENS3_INS2_11PropertyKeyEEENS2_13MutableHandleIS7_EE (0x10c9b3009)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/NativeObject.cpp:2243
 0:09.84 pid:73015   28: script::dom::windowproxy::get::h4e0fd302c9e1d573 (0x109d8712c)
 0:09.84 pid:73015              at components/script/dom/windowproxy.rs:897
 0:09.84 pid:73015   29: _ZNK19WrapperProxyHandler3getEP9JSContextN2JS6HandleIP8JSObjectEENS3_INS2_5ValueEEENS3_INS2_11PropertyKeyEEENS2_13MutableHandleIS7_EE (0x10c8437c3)
 0:09.84 pid:73015   30: _ZN2js5Proxy3getEP9JSContextN2JS6HandleIP8JSObjectEENS4_INS3_5ValueEEENS4_INS3_11PropertyKeyEEENS3_13MutableHandleIS8_EE (0x10cb3f599)
 0:09.84 pid:73015   31: _ZL11RevokeProxyP9JSContextjPN2JS5ValueE (0x10cb49393)
 0:09.84 pid:73015   32: _Z9js_strtodIhEbP9JSContextPKT_S4_PS4_Pd (0x10cb34ccd)
 0:09.84 pid:73015   33: _ZN2js5Proxy3getEP9JSContextN2JS6HandleIP8JSObjectEENS4_INS3_5ValueEEENS4_INS3_11PropertyKeyEEENS3_13MutableHandleIS8_EE (0x10cb3f599)
 0:09.84 pid:73015   34: _ZL9InterpretP9JSContextRN2js8RunStateE (0x10c86947b)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/ObjectOperations-inl.h:114
 0:09.84 pid:73015   35: _ZN2js9RunScriptEP9JSContextRNS_8RunStateE (0x10c860b70)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:422
 0:09.84 pid:73015   36: _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructE (0x10c871812)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:562
 0:09.84 pid:73015   37: _ZN2js4CallEP9JSContextN2JS6HandleINS2_5ValueEEES5_RKNS_13AnyInvokeArgsENS2_13MutableHandleIS4_EE (0x10c871cc6)
 0:09.84 pid:73015   38: _ZN2js9fun_applyEP9JSContextjPN2JS5ValueE (0x10c97456a)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/JSFunction.cpp:1180
 0:09.84 pid:73015   39: _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructE (0x10c871527)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:442
 0:09.84 pid:73015   40: _ZL9InterpretP9JSContextRN2js8RunStateE (0x10c86af39)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:593
 0:09.84 pid:73015   41: _ZN2js9RunScriptEP9JSContextRNS_8RunStateE (0x10c860b70)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:422
 0:09.84 pid:73015   42: _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructE (0x10c871812)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:562
 0:09.84 pid:73015   43: _ZN2js4CallEP9JSContextN2JS6HandleINS2_5ValueEEES5_RKNS_13AnyInvokeArgsENS2_13MutableHandleIS4_EE (0x10c871cc6)
 0:09.84 pid:73015   44: _ZN2js9fun_applyEP9JSContextjPN2JS5ValueE (0x10c97456a)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/JSFunction.cpp:1180
 0:09.84 pid:73015   45: _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructE (0x10c871527)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:442
 0:09.84 pid:73015   46: _ZL9InterpretP9JSContextRN2js8RunStateE (0x10c86af39)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:593
 0:09.84 pid:73015   47: _ZN2js9RunScriptEP9JSContextRNS_8RunStateE (0x10c860b70)
 0:09.84 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:422
 0:09.84 pid:73015   48: _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructE (0x10c871812)
 0:09.85 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:562
 0:09.85 pid:73015   49: _ZN2js4CallEP9JSContextN2JS6HandleINS2_5ValueEEES5_RKNS_13AnyInvokeArgsENS2_13MutableHandleIS4_EE (0x10c871cc6)
 0:09.85 pid:73015   50: _ZN2js9fun_applyEP9JSContextjPN2JS5ValueE (0x10c97456a)
 0:09.85 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/JSFunction.cpp:1180
 0:09.85 pid:73015   51: _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructE (0x10c871527)
 0:09.85 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:442
 0:09.85 pid:73015   52: _ZL9InterpretP9JSContextRN2js8RunStateE (0x10c86af39)
 0:09.85 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:593
 0:09.85 pid:73015   53: _ZN2js9RunScriptEP9JSContextRNS_8RunStateE (0x10c860b70)
 0:09.85 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:422
 0:09.85 pid:73015   54: _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructE (0x10c871812)
 0:09.85 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/vm/Interpreter.cpp:562
 0:09.85 pid:73015   55: _ZN2js4CallEP9JSContextN2JS6HandleINS2_5ValueEEES5_RKNS_13AnyInvokeArgsENS2_13MutableHandleIS4_EE (0x10c871cc6)
 0:09.85 pid:73015   56: _Z20JS_CallFunctionValueP9JSContextN2JS6HandleIP8JSObjectEENS2_INS1_5ValueEEERKNS1_16HandleValueArrayENS1_13MutableHandleIS6_EE (0x10cb05c23)
 0:09.85 pid:73015              at /Users/jdm/.cargo/git/checkouts/mozjs-fa11ffc7d4f1cc2d/dd175ee/mozjs/js/src/jsapi.cpp:2560
 0:09.85 pid:73015   57: mozjs::rust::wrappers::JS_CallFunctionValue::hf3041f8df4099754 (0x10b4dc9d7)
 0:09.85 pid:73015              at /Users/jdm/.cargo/git/checkouts/rust-mozjs-8611526964119dd6/2ef1de9/src/rust.rs:1368
 0:09.85 pid:73015   58: script::dom::bindings::codegen::Bindings::FunctionBinding::Function::Call::h761546496eb56a37 (0x10c4d02af)
 0:09.85 pid:73015              at /Users/jdm/src/master-servo/target/debug/build/script-decac3ca7e8f26ff/out/Bindings/FunctionBinding.rs:317
 0:09.85 pid:73015   59: script::dom::bindings::codegen::Bindings::FunctionBinding::Function::Call_::h0f1e1ede65b52f19 (0x10c4cf437)
 0:09.85 pid:73015              at /Users/jdm/src/master-servo/target/debug/build/script-decac3ca7e8f26ff/out/Bindings/FunctionBinding.rs:289
 0:09.85 pid:73015   60: script::timers::JsTimerTask::invoke::h0bc3fad00138ec60 (0x10b5ecec6)
 0:09.85 pid:73015              at components/script/timers.rs:526
 0:09.85 pid:73015   61: script::timers::OneshotTimerCallback::invoke::hdb4fb66a295e19d0 (0x10b5e98e2)
 0:09.85 pid:73015              at components/script/timers.rs:82
 0:09.85 pid:73015   62: script::timers::OneshotTimers::fire_timer::hb9469f5017aa3e81 (0x10b5ead1f)
 0:09.85 pid:73015              at components/script/timers.rs:214
 0:09.85 pid:73015   63: script::dom::globalscope::GlobalScope::fire_timer::h4f583152ebb2b92d (0x10c0d81f8)
 0:09.85 pid:73015              at components/script/dom/globalscope.rs:635
 0:09.85 pid:73015   64: script::dom::window::Window::handle_fire_timer::h71d11cea674a70c5 (0x10b5db738)
 0:09.85 pid:73015              at components/script/dom/window.rs:1917
 0:09.85 pid:73015   65: script::script_thread::ScriptThread::handle_timer_event::hc759606fb778a84b (0x10beb7eed)
 0:09.85 pid:73015              at components/script/script_thread.rs:1993
 0:09.91 pid:73015   66: script::script_thread::ScriptThread::handle_msgs::{{closure}}::hca720bf775dde9e8 (0x10beb0b64)
 0:09.91 pid:73015              at components/script/script_thread.rs:1551
 0:09.91 pid:73015   67: script::script_thread::ScriptThread::profile_event::h0da42cdce66c2fc5 (0x10beb2b95)
 0:09.91 pid:73015              at components/script/script_thread.rs:1785
 0:09.91 pid:73015   68: script::script_thread::ScriptThread::handle_msgs::h9b9dcf5c579a5741 (0x10beaeba2)
 0:09.91 pid:73015              at components/script/script_thread.rs:1543
 0:09.91 pid:73015   69: script::script_thread::ScriptThread::start::h5956d51347322f1b (0x10beac5a0)
 0:09.91 pid:73015              at components/script/script_thread.rs:1376
 0:09.91 pid:73015   70: <script::script_thread::ScriptThread as script_traits::ScriptThreadFactory>::create::{{closure}}::{{closure}}::h231b7052c5f77693 (0x10bea5d85)
 0:09.91 pid:73015              at components/script/script_thread.rs:803
 0:09.91 pid:73015   71: profile_traits::mem::ProfilerChan::run_with_memory_reporting::h58e2364e01b4c089 (0x10a2c3127)
 0:09.91 pid:73015              at /Users/jdm/src/master-servo/components/profile_traits/mem.rs:88
 0:09.91 pid:73015   72: <script::script_thread::ScriptThread as script_traits::ScriptThreadFactory>::create::{{closure}}::h5fe693fcddba0933 (0x10bea64df)
 0:09.91 pid:73015              at components/script/script_thread.rs:801
 0:09.91 pid:73015   73: std::sys_common::backtrace::__rust_begin_short_backtrace::h7eb0ae8af2e4e939 (0x10b488d93)
 0:09.91 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libstd/sys_common/backtrace.rs:126
 0:09.91 pid:73015   74: std::thread::Builder::spawn_unchecked::{{closure}}::{{closure}}::h5a5bf139288034a6 (0x10a5347e3)
 0:09.91 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libstd/thread/mod.rs:470
 0:09.91 pid:73015   75: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::hdeb89e1836ae2f31 (0x10bfbd673)
 0:09.91 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libstd/panic.rs:315
 0:09.91 pid:73015   76: std::panicking::try::do_call::hd71476bc8925af5a (0x109c15635)
 0:09.91 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libstd/panicking.rs:292
 0:09.91 pid:73015   77: __rust_maybe_catch_panic (0x110e3a39f)
 0:09.91 pid:73015              at src/libpanic_unwind/lib.rs:80
 0:09.91 pid:73015   78: std::panicking::try::h1e0cc08a8165bb32 (0x1099c6ac5)
 0:09.91 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libstd/panicking.rs:271
 0:09.91 pid:73015   79: std::panic::catch_unwind::hf679d78bb215f68c (0x10c045eb3)
 0:09.91 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libstd/panic.rs:394
 0:09.91 pid:73015   80: std::thread::Builder::spawn_unchecked::{{closure}}::h65947377e0e93c47 (0x10a53319c)
 0:09.91 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libstd/thread/mod.rs:469
 0:09.91 pid:73015   81: core::ops::function::FnOnce::call_once{{vtable.shim}}::hc3e67058b13d58f4 (0x10b074025)
 0:09.91 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/libcore/ops/function.rs:227
 0:09.91 pid:73015   82: <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h05d1dd9ed3001f9a (0x110e220be)
 0:09.91 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/liballoc/boxed.rs:922
 0:09.91 pid:73015   83: <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h5844bd7c60199346 (0x110e3989e)
 0:09.91 pid:73015              at /rustc/084beb83e0e87d673d5fabc844d28e8e8ae2ab4c/src/liballoc/boxed.rs:922
 0:09.91 pid:73015       std::sys_common::thread::start_thread::h240f5fe6d431024b
 0:09.91 pid:73015              at src/libstd/sys_common/thread.rs:13
 0:09.91 pid:73015       std::sys::unix::thread::Thread::new::thread_start::h31206210a464c44a
 0:09.91 pid:73015              at src/libstd/sys/unix/thread.rs:79
 0:09.91 pid:73015   84: <unknown> (0x7fff7d6262eb)
 0:09.91 pid:73015   85: <unknown> (0x7fff7d629249)
 0:09.91 pid:73015 [2019-10-16T14:14:50Z ERROR servo] called `Option::unwrap()` on a `None` value
 0:09.91 pid:73015 Pipeline failed in hard-fail mode.  Crashing!

Window::window_proxy has this comment:

"    /// This can panic if it is called after the browsing context has been discarded"

[jdm]

The solution might be to follow the specification better based on whatwg/html#4410.

[gterzian]

I think this is the same as #24591, although it might still be worth it to implement the spec in a more compliant way as linked to.