Use the Navigator's frame in navigator.serviceWorker and associated container.

Source/modules/serviceworkers/ServiceWorkerContainer.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 101 matching lines @@
 
     m_provider->unregisterServiceWorker(patternURL, new CallbackPromiseAdapter<ServiceWorker, ServiceWorkerError>(resolver, executionContext));
     return promise;
 }
 
 ServiceWorkerContainer::ServiceWorkerContainer(ExecutionContext* executionContext)
     : m_provider(0)
 {
     ScriptWrappable::init(this);
 
+    if (!executionContext)
+        return;
+
     if (ServiceWorkerContainerClient* client = ServiceWorkerContainerClient::from(executionContext)) {
         m_provider = client->provider();
         if (m_provider)
             m_provider->setClient(this);
     }
 }
 
 } // namespace WebCore