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

Source/platform/mac/ThemeMac.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 18 matching lines @@
 #include "platform/Theme.h"
 
 @interface NSFont(WebCoreTheme)
 - (NSString*)webCoreFamilyName;
 @end
 
 namespace blink {
 
 class ThemeMac : public Theme {
 public:
-    ThemeMac() { }
-    virtual ~ThemeMac() { }
+    ThemeMac() {}
+    ~ThemeMac() override {}
 
     virtual int baselinePositionAdjustment(ControlPart) const;
 
     virtual FontDescription controlFont(ControlPart, const FontDescription&, float zoomFactor) const;
 
     virtual LengthSize controlSize(ControlPart, const FontDescription&, const LengthSize&, float zoomFactor) const;
     virtual LengthSize minimumControlSize(ControlPart, const FontDescription&, float zoomFactor) const;
 
     virtual LengthBox controlPadding(ControlPart, const FontDescription&, const LengthBox& zoomedBox, float zoomFactor) const;
     virtual LengthBox controlBorder(ControlPart, const FontDescription&, const LengthBox& zoomedBox, float zoomFactor) const;
@@ skipping 19 matching lines @@
     // drawWithFrameDrawsFocusRing() returns true (otherwise, the focus ring's
     // bounds could be accurately computed with -[NSCell focusRingMaskBoundsForFrame:inView:]).
     static PLATFORM_EXPORT IntRect inflateRectForFocusRing(const IntRect&);
 
     static PLATFORM_EXPORT bool drawWithFrameDrawsFocusRing();
 };
 
 } // namespace blink
 
 #endif // ThemeMac_h