properly shutdown dedicated workers when the owning scope shuts-down

components/script/dom/dedicatedworkerglobalscope.rs

@@ -460,6 +460,7 @@ impl DedicatedWorkerGlobalScope {
                         parent_sender,
                         CommonScriptMsg::CollectReports,
                     );
+                scope.clear_js_runtime();
             })
             .expect("Thread spawning failed")
     }

components/script/dom/globalscope.rs

@@ -794,9 +794,18 @@ impl GlobalScope {
     }
 
     /// Remove the routers for ports and broadcast-channels.
-    pub fn remove_web_messaging_infra(&self) {
+    /// Drain the list of workers.
+    pub fn remove_web_messaging_and_dedicated_workers_infra(&self) {
         self.remove_message_ports_router();
         self.remove_broadcast_channel_router();
+
+        // Drop each ref to a worker explicitly now,
+        // which will send a shutdown signal,
+        // and join on the worker thread.
+        self.list_auto_close_worker
+            .borrow_mut()
+            .drain(0..)
+            .for_each(|worker| drop(worker));
     }
 
     /// Update our state to un-managed,

components/script/dom/window.rs

@@ -1441,8 +1441,8 @@ impl Window {
     }
 
     pub fn clear_js_runtime(&self) {
-        // Remove the infra for managing messageports and broadcast channels.
+        self.upcast::<GlobalScope>()
-        self.upcast::<GlobalScope>().remove_web_messaging_infra();
+            .remove_web_messaging_and_dedicated_workers_infra();
 
         // Clean up any active promises
         // https://github.com/servo/servo/issues/15318