Break two classes defined in json_value_serializer.cc, .h into separate files.

chrome/common/extensions/extension_unpacker.cc

 // 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.
 
 #include "chrome/common/extensions/extension_unpacker.h"
 
 #include <set>
 
 #include "base/file_util.h"
-#include "base/json/json_value_serializer.h"
+#include "base/json/json_file_value_serializer.h"
 #include "base/memory/scoped_handle.h"
 #include "base/scoped_temp_dir.h"
 #include "base/string_util.h"
 #include "base/threading/thread.h"
 #include "base/utf_string_conversions.h"
 #include "base/values.h"
 #include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_constants.h"
 #include "chrome/common/extensions/extension_file_util.h"
 #include "chrome/common/extensions/extension_l10n_util.h"
@@ skipping 298 matching lines @@
     return false;
   }
   parsed_catalogs_->Set(dir_name, root.release());
 
   return true;
 }
 
 void ExtensionUnpacker::SetError(const std::string &error) {
   error_message_ = UTF8ToUTF16(error);
 }