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

base/json/json_reader.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.
 //
 // A JSON parser.  Converts strings of JSON into a Value object (see
 // base/values.h).
 // http://www.ietf.org/rfc/rfc4627.txt?number=4627
 //
 // Known limitations/deviations from the RFC:
 // - Only knows how to parse ints within the range of a signed 32 bit int and
 //   decimal numbers within a double.
 // - Assumes input is encoded as UTF8.  The spec says we should allow UTF-16
 //   (BE or LE) and UTF-32 (BE or LE) as well.
 // - We limit nesting to 100 levels to prevent stack overflow (this is allowed
 //   by the RFC).
 // - A Unicode FAQ ("http://unicode.org/faq/utf_bom.html") writes a data
 //   stream may start with a Unicode Byte-Order-Mark (U+FEFF), i.e. the input
 //   UTF-8 string for the JSONReader::JsonToValue() function may start with a
 //   UTF-8 BOM (0xEF, 0xBB, 0xBF).
 //   To avoid the function from mis-treating a UTF-8 BOM as an invalid
 //   character, the function skips a Unicode BOM at the beginning of the
 //   Unicode string (converted from the input UTF-8 string) before parsing it.
 //
 // TODO(tc): Add a parsing option to to relax object keys being wrapped in
 //   double quotes
 // TODO(tc): Add an option to disable comment stripping
 
 #ifndef BASE_JSON_JSON_READER_H_
 #define BASE_JSON_JSON_READER_H_
-#pragma once
 
 #include <string>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/string_piece.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
 class Value;
@@ skipping 86 matching lines @@
   // numbers if appropriate.
   std::string GetErrorMessage() const;
 
  private:
   scoped_ptr<internal::JSONParser> parser_;
 };
 
 }  // namespace base
 
 #endif  // BASE_JSON_JSON_READER_H_