Bug 1517896 - Fix shell context shutdown ordering, r=jonco

--HG--
extra : rebase_source : 530a05250ed4b02206b62d4499fda8cdb5c5462e
extra : amend_source : 7f28a75c5d1abea4bc1076c92fa48fae964ae054

Author: hotsphink

js/src/shell/js.cpp

@@ -3978,8 +3978,9 @@ static void WorkerMain(WorkerInput* input) {
   auto guard = mozilla::MakeScopeExit([&] {
     CancelOffThreadJobsForContext(cx);
     sc->markObservers.reset();
-    JS_DestroyContext(cx);
+    JS_SetContextPrivate(cx, nullptr);
     js_delete(sc);
+    JS_DestroyContext(cx);
     js_delete(input);
   });
 
@@ -10986,6 +10987,8 @@ int main(int argc, char** argv, char** envp) {
 
   CancelOffThreadJobsForRuntime(cx);
 
+  JS_SetContextPrivate(cx, nullptr);
+  sc.reset();
   JS_DestroyContext(cx);
   return result;
 }

js/src/vm/JSContext.cpp

@@ -184,15 +184,19 @@ void js::DestroyContext(JSContext* cx) {
 
   cx->jobQueue = nullptr;
   cx->internalJobQueue = nullptr;
+  SetContextProfilingStack(cx, nullptr);
+
+  JSRuntime* rt = cx->runtime();
 
   // Flush promise tasks executing in helper threads early, before any parts
   // of the JSRuntime that might be visible to helper threads are torn down.
-  cx->runtime()->offThreadPromiseState.ref().shutdown(cx);
+  rt->offThreadPromiseState.ref().shutdown(cx);
 
   // Destroy the runtime along with its last context.
-  cx->runtime()->destroyRuntime();
-  js_delete(cx->runtime());
+  js::AutoNoteSingleThreadedRegion nochecks;
+  rt->destroyRuntime();
   js_delete_poison(cx);
+  js_delete_poison(rt);
 }
 
 void JS::RootingContext::checkNoGCRooters() {