Fix virtual/override/final usage in the rest of Source/core/.

Source/core/workers/WorkerNavigator.h

 /*
  * Copyright (C) 2008 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 28 matching lines @@
 class WorkerNavigator final : public GarbageCollectedFinalized<WorkerNavigator>, public ScriptWrappable, public NavigatorCPU, public NavigatorID, public NavigatorOnLine, public HeapSupplementable<WorkerNavigator> {
     DEFINE_WRAPPERTYPEINFO();
     USING_GARBAGE_COLLECTED_MIXIN(WorkerNavigator);
 public:
     static WorkerNavigator* create(const String& userAgent)
     {
         return new WorkerNavigator(userAgent);
     }
     virtual ~WorkerNavigator();
 
-    virtual String userAgent() const override;
+    String userAgent() const override;
 
     DECLARE_TRACE();
 
 private:
     explicit WorkerNavigator(const String&);
 
     String m_userAgent;
 };
 
 } // namespace blink
 
 #endif // WorkerNavigator_h