Add more missing closing namespace comments.

third_party/WebKit/Source/core/html/shadow/SliderThumbElement.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google 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 71 matching lines @@
 class SliderContainerElement final : public HTMLDivElement {
 public:
     DECLARE_NODE_FACTORY(SliderContainerElement);
 
 private:
     explicit SliderContainerElement(Document&);
     LayoutObject* createLayoutObject(const ComputedStyle&) override;
     const AtomicString& shadowPseudoId() const override;
 };
 
-}
+} // namespace blink
 
 #endif