base: Add/Fix namespace closing comments.

base/strings/nullable_string16.h

 // Copyright (c) 2010 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 BASE_STRINGS_NULLABLE_STRING16_H_
 #define BASE_STRINGS_NULLABLE_STRING16_H_
 
 #include <iosfwd>
 
 #include "base/base_export.h"
@@ skipping 23 matching lines @@
   return a.is_null() == b.is_null() && a.string() == b.string();
 }
 
 inline bool operator!=(const NullableString16& a, const NullableString16& b) {
   return !(a == b);
 }
 
 BASE_EXPORT std::ostream& operator<<(std::ostream& out,
                                      const NullableString16& value);
 
-}  // namespace
+}  // namespace base
 
 #endif  // BASE_STRINGS_NULLABLE_STRING16_H_