Add more missing closing namespace comments.

third_party/WebKit/Source/core/dom/DocumentStatisticsCollector.h

 // Copyright 2015 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 DocumentStatisticsCollector_h
 #define DocumentStatisticsCollector_h
 
 #include "core/CoreExport.h"
 
 namespace blink {
 
 class Document;
 struct WebDistillabilityFeatures;
 
 class CORE_EXPORT DocumentStatisticsCollector {
 public:
     static WebDistillabilityFeatures collectStatistics(Document&);
 };
 
-}
+} // namespace blink
 
 #endif