Fix virtual/override/final usage in Source/platform/.

Source/platform/scroll/ScrollbarThemeMacCommon.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 19 matching lines @@
 #include "platform/scroll/ScrollbarTheme.h"
 
 class SkCanvas;
 
 namespace blink {
 
 class Pattern;
 
 class PLATFORM_EXPORT ScrollbarThemeMacCommon : public ScrollbarTheme {
 public:
-    virtual ~ScrollbarThemeMacCommon();
+    ~ScrollbarThemeMacCommon() override;
 
-    virtual void registerScrollbar(ScrollbarThemeClient*) override;
-    virtual void unregisterScrollbar(ScrollbarThemeClient*) override;
+    void registerScrollbar(ScrollbarThemeClient*) override;
+    void unregisterScrollbar(ScrollbarThemeClient*) override;
     void preferencesChanged(float initialButtonDelay, float autoscrollButtonDelay, NSScrollerStyle preferredScrollerStyle, bool redraw);
 
-    virtual bool supportsControlTints() const override { return true; }
+    bool supportsControlTints() const override { return true; }
 
-    virtual double initialAutoscrollTimerDelay() override;
-    virtual double autoscrollTimerDelay() override;
+    double initialAutoscrollTimerDelay() override;
+    double autoscrollTimerDelay() override;
 
-    virtual void paintTickmarks(GraphicsContext*, ScrollbarThemeClient*, const IntRect&) override;
+    void paintTickmarks(GraphicsContext*, ScrollbarThemeClient*, const IntRect&) override;
 
     static NSScrollerStyle recommendedScrollerStyle();
 
     static bool isOverlayAPIAvailable();
 
 protected:
-    virtual int maxOverlapBetweenPages() override { return 40; }
+    int maxOverlapBetweenPages() override { return 40; }
 
-    virtual bool shouldDragDocumentInsteadOfThumb(ScrollbarThemeClient*, const PlatformMouseEvent&) override;
+    bool shouldDragDocumentInsteadOfThumb(ScrollbarThemeClient*, const PlatformMouseEvent&) override;
     int scrollbarPartToHIPressedState(ScrollbarPart);
 
     virtual void updateButtonPlacement() { }
 
     void paintGivenTickmarks(SkCanvas*, ScrollbarThemeClient*, const IntRect&, const Vector<IntRect>&);
 
     RefPtr<Pattern> m_overhangPattern;
 };
 
 }
 
 #endif // ScrollbarThemeMacCommon_h