Add more missing closing namespace comments.

third_party/WebKit/Source/core/xml/XPathExpressionNode.cpp

 /*
  * Copyright 2005 Frerich Raabe <raabe@kde.org>
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * 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.
@@ skipping 38 matching lines @@
 Expression::~Expression()
 {
 }
 
 DEFINE_TRACE(Expression)
 {
     visitor->trace(m_subExpressions);
     ParseNode::trace(visitor);
 }
 
-}
-}
+} // namespace XPath
+} // namespace blink