Auto merge of #11244 - Ms2ger:catch-panics-workers, r=nox

Report panics in web worker threads.

Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data:
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy --faster` does not report any errors
- [ ] These changes fix #11234 (github issue number if applicable).

Either:
- [x] There are tests for these changes OR
- [ ] These changes do not require tests because _____

Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process.

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components/script/dom/bindings/global.rs

@@ -18,7 +18,7 @@ use ipc_channel::ipc::IpcSender;
 use js::jsapi::{CurrentGlobalOrNull, GetGlobalForObjectCrossCompartment};
 use js::jsapi::{JSContext, JSObject, JS_GetClass, MutableHandleValue};
 use js::{JSCLASS_IS_DOMJSCLASS, JSCLASS_IS_GLOBAL};
-use msg::constellation_msg::{ConstellationChan, PipelineId};
+use msg::constellation_msg::{ConstellationChan, PanicMsg, PipelineId};
 use net_traits::ResourceThread;
 use profile_traits::mem;
 use script_runtime::{CommonScriptMsg, ScriptChan, ScriptPort};
@@ -263,6 +263,14 @@ impl<'a> GlobalRef<'a> {
             GlobalRef::Worker(ref worker) => worker.reflector(),
         }
     }
+
+    /// Returns an `IpcSender` to report panics on.
+    pub fn panic_chan(&self) -> &IpcSender<PanicMsg> {
+        match *self {
+            GlobalRef::Window(ref window) => window.panic_chan(),
+            GlobalRef::Worker(ref worker) => worker.panic_chan(),
+        }
+    }
 }
 
 impl GlobalRoot {