Update AbstractWorker, Worker and SharedWorker to match the spec

Source/core/workers/Worker.h

Index: Source/core/workers/Worker.h
diff --git a/Source/core/workers/Worker.h b/Source/core/workers/Worker.h
index 64100b03c40ee3018ee3b37e38a9f24882e76d8e..f01c774017771e9d3d22180677aa89babda75072 100644
--- a/Source/core/workers/Worker.h
+++ b/Source/core/workers/Worker.h
@@ -47,7 +47,7 @@ namespace WebCore {
 
     typedef int ExceptionCode;
 
-    class Worker : public AbstractWorker, private WorkerScriptLoaderClient {
+    class Worker : public AbstractWorker, public ScriptWrappable, public ActiveDOMObject, private WorkerScriptLoaderClient {
     public:
         static PassRefPtr<Worker> create(ScriptExecutionContext*, const String& url, ExceptionCode&);
         virtual ~Worker();
@@ -61,6 +61,8 @@ namespace WebCore {
         virtual bool canSuspend() const OVERRIDE;
         virtual void stop() OVERRIDE;
         virtual bool hasPendingActivity() const OVERRIDE;
+        virtual void contextDestroyed() OVERRIDE;
+        virtual ScriptExecutionContext* scriptExecutionContext() const OVERRIDE { return ActiveDOMObject::scriptExecutionContext(); }
     
         DEFINE_ATTRIBUTE_EVENT_LISTENER(message);