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

Source/core/layout/line/TrailingFloatsRootInlineBox.h

 /*
  * Copyright (C) 2010 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 21 matching lines @@
 
 class TrailingFloatsRootInlineBox final : public RootInlineBox {
 public:
     TrailingFloatsRootInlineBox(LayoutBlockFlow& block)
         : RootInlineBox(block)
     {
         setHasVirtualLogicalHeight();
     }
 
 private:
-    virtual LayoutUnit virtualLogicalHeight() const override { return 0; }
+    LayoutUnit virtualLogicalHeight() const override { return 0; }
 };
 
 } // namespace blink
 
 #endif // TrailingFloatsRootInlineBox_h