Update AbstractWorker, Worker and SharedWorker to match the spec

Source/core/workers/Worker.cpp

Index: Source/core/workers/Worker.cpp
diff --git a/Source/core/workers/Worker.cpp b/Source/core/workers/Worker.cpp
index 00389db9f479083f5c38cc9af20a1c0905ce4be3..6a12ccd5addd371a261431a9369fe6108435f54c 100644
--- a/Source/core/workers/Worker.cpp
+++ b/Source/core/workers/Worker.cpp
@@ -48,7 +48,7 @@
 namespace WebCore {
 
 inline Worker::Worker(ScriptExecutionContext* context)
-    : AbstractWorker(context)
+    : ActiveDOMObject(context)
     , m_contextProxy(WorkerContextProxy::create(this))
 {
     ScriptWrappable::init(this);
@@ -139,4 +139,9 @@ void Worker::notifyFinished()
     unsetPendingActivity(this);
 }
 
+void Worker::contextDestroyed()
+{
+    ActiveDOMObject::contextDestroyed();
+}
+
 } // namespace WebCore