Add missing isolatedCopy() call in ServiceWorkerThreadProxy::fireMess…

…ageEvent()

https://bugs.webkit.org/show_bug.cgi?id=273918

Reviewed by Brady Eidson.

ServiceWorkerThreadProxy::fireMessageEvent() is dispatching from the
WebSWContextManagerConnection queue to the ServiceWorker thread, yet, it was
failing to call isolatedCopy() on the ServiceWorkerOrClientData it is
capturing.

* Source/WebCore/workers/service/context/ServiceWorkerThreadProxy.cpp:
(WebCore::ServiceWorkerThreadProxy::fireMessageEvent):

Canonical link: https://commits.webkit.org/278563@main

Source/WebCore/workers/service/context/ServiceWorkerThreadProxy.cpp

@@ -329,7 +329,7 @@ void ServiceWorkerThreadProxy::fireMessageEvent(MessageWithMessagePorts&& messag
         protectedThis->thread().willPostTaskToFireMessageEvent();
     });
 
-    thread().runLoop().postTask([this, protectedThis = Ref { *this }, message = WTFMove(message), sourceData = WTFMove(sourceData)](auto&) mutable {
+    thread().runLoop().postTask([this, protectedThis = Ref { *this }, message = WTFMove(message), sourceData = crossThreadCopy(WTFMove(sourceData))](auto&) mutable {
         thread().queueTaskToPostMessage(WTFMove(message), WTFMove(sourceData));
     });
 }