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

Source/core/timing/Performance.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2012 Intel 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.
@@ skipping 31 matching lines @@
 namespace blink {
 
 class CORE_EXPORT Performance final : public PerformanceBase, public DOMWindowProperty {
     DEFINE_WRAPPERTYPEINFO();
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(Performance);
 public:
     static Performance* create(LocalFrame* frame)
     {
         return new Performance(frame);
     }
-    virtual ~Performance();
+    ~Performance() override;
 
-    virtual ExecutionContext* executionContext() const override;
+    ExecutionContext* executionContext() const override;
 
     MemoryInfo* memory();
     PerformanceNavigation* navigation() const;
     PerformanceTiming* timing() const override;
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     explicit Performance(LocalFrame*);
 
     mutable Member<PerformanceNavigation> m_navigation;
     mutable Member<PerformanceTiming> m_timing;
 };
 
 } // namespace blink
 
 #endif // Performance_h