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

chrome/installer/util/master_preferences.cc

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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/installer/util/master_preferences.h"
 
 #include "base/environment.h"
 #include "base/file_util.h"
-#include "base/json/json_value_serializer.h"
+#include "base/json/json_string_value_serializer.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/path_service.h"
 #include "base/string_util.h"
 #include "chrome/installer/util/master_preferences_constants.h"
 #include "chrome/installer/util/util_constants.h"
 #include "googleurl/src/gurl.h"
 
 namespace {
 
@@ skipping 239 matching lines @@
 bool MasterPreferences::GetExtensionsBlock(DictionaryValue** extensions) const {
   return master_dictionary_->GetDictionary(
       master_preferences::kExtensionsBlock, extensions);
 }
 
 // static
 const MasterPreferences& MasterPreferences::ForCurrentProcess() {
   return g_master_preferences.Get();
 }
 }  // installer_util