Update platform classes to use OVERRIDE / FINAL when needed

Source/platform/SharedTimer.h

 /*
  * Copyright (C) 2006 Apple Computer, 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 36 matching lines @@
     virtual void stop() = 0;
 };
 
 
 PLATFORM_EXPORT void setSharedTimerFiredFunction(void (*)());
 PLATFORM_EXPORT void setSharedTimerFireInterval(double);
 PLATFORM_EXPORT void stopSharedTimer();
 
 class PLATFORM_EXPORT MainThreadSharedTimer : public SharedTimer {
 public:
-    virtual void setFiredFunction(void (*function)())
+    virtual void setFiredFunction(void (*function)()) OVERRIDE
     {
         setSharedTimerFiredFunction(function);
     }
 
-    virtual void setFireInterval(double interval)
+    virtual void setFireInterval(double interval) OVERRIDE
     {
         setSharedTimerFireInterval(interval);
     }
 
-    virtual void stop()
+    virtual void stop() OVERRIDE
     {
         stopSharedTimer();
     }
 };
 
 } // namespace WebCore
 
 #endif // SharedTimer_h