Remove #pragma once. Just from base/ for now.

base/json/json_parser.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.
 
 #ifndef BASE_JSON_JSON_PARSER_H_
 #define BASE_JSON_JSON_PARSER_H_
-#pragma once
 
 #include <string>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/json/json_reader.h"
 #include "base/string_piece.h"
 
 #if !defined(OS_CHROMEOS)
@@ skipping 246 matching lines @@
   FRIEND_TEST_ALL_PREFIXES(JSONParserTest, ConsumeNumbers);
   FRIEND_TEST_ALL_PREFIXES(JSONParserTest, ErrorMessages);
 
   DISALLOW_COPY_AND_ASSIGN(JSONParser);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_JSON_JSON_PARSER_H_