Add more missing closing namespace comments.

third_party/WebKit/Source/core/html/HTMLIFrameElementSandbox.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef HTMLIFrameElementSandbox_h
 #define HTMLIFrameElementSandbox_h
 
 #include "core/dom/DOMSettableTokenList.h"
 
 namespace blink {
 
 class HTMLIFrameElementSandbox final : public DOMSettableTokenList {
 public:
     static PassRefPtrWillBeRawPtr<HTMLIFrameElementSandbox> create(DOMSettableTokenListObserver* observer = nullptr)
     {
         return adoptRefWillBeNoop(new HTMLIFrameElementSandbox(observer));
     }
 
     ~HTMLIFrameElementSandbox() override;
 
 private:
     explicit HTMLIFrameElementSandbox(DOMSettableTokenListObserver*);
     bool validateTokenValue(const AtomicString&, ExceptionState&) const override;
 };
 
-}
+} // namespace blink
 
 #endif