Fix virtual/override/final usage in Source/core/layout/.

Source/core/layout/LayoutVTTCue.h

 /*
  * Copyright (C) 2012 Victor Carbune (victor@rosedu.org)
  *
  * 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 21 matching lines @@
 namespace blink {
 
 class VTTCue;
 class VTTCueBox;
 
 class LayoutVTTCue final : public LayoutBlockFlow {
 public:
     explicit LayoutVTTCue(VTTCueBox*);
 
 private:
-    virtual void layout() override;
+    void layout() override;
 
     void adjustForTopAndBottomMarginBorderAndPadding();
     void repositionCueSnapToLinesNotSet();
 
     VTTCue* m_cue;
 };
 
 } // namespace blink
 
 #endif // LayoutVTTCue_h