Add missing closing namespace comments to wtf.

base/strings/string_piece.h

 // Copyright (c) 2012 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.
 // Copied from strings/stringpiece.h with modifications
 //
 // A string-like object that points to a sized piece of memory.
 //
 // You can use StringPiece as a function or method parameter.  A StringPiece
 // parameter can receive a double-quoted string literal argument, a "const
 // char*" argument, a string argument, or a StringPiece argument with no data
@@ skipping 446 matching lines @@
     HASH_STRING_PIECE(base::StringPiece, sp);
   }
 };
 template<>
 struct hash<base::StringPiece16> {
   std::size_t operator()(const base::StringPiece16& sp16) const {
     HASH_STRING_PIECE(base::StringPiece16, sp16);
   }
 };
 
-}  // namespace BASE_HASH_NAMESPACE
+}  // namespace base_hash
 
 #endif  // BASE_STRINGS_STRING_PIECE_H_