Use std::unique_ptr for base::DictionaryValue and base::ListValue's internal store.

chrome/browser/plugins/plugin_prefs.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/browser/plugins/plugin_prefs.h"
 
 #include <stddef.h>
 
 #include <memory>
 #include <string>
@@ skipping 315 matching lines @@
       cur_internal_dir != last_internal_dir) {
     update_internal_dir = true;
     prefs_->SetFilePath(
         prefs::kPluginsLastInternalDirectory, cur_internal_dir);
   }
 
   {  // Scoped update of prefs::kPluginsPluginsList.
     ListPrefUpdate update(prefs_, prefs::kPluginsPluginsList);
     base::ListValue* saved_plugins_list = update.Get();
     if (saved_plugins_list && !saved_plugins_list->empty()) {
-      for (base::Value* plugin_value : *saved_plugins_list) {
-        if (!plugin_value->IsType(base::Value::TYPE_DICTIONARY)) {
+      for (const auto& plugin_value : *saved_plugins_list) {
+        base::DictionaryValue* plugin;
+        if (!plugin_value->GetAsDictionary(&plugin)) {
           LOG(WARNING) << "Invalid entry in " << prefs::kPluginsPluginsList;
           continue;  // Oops, don't know what to do with this item.
         }
 
-        base::DictionaryValue* plugin =
-            static_cast<base::DictionaryValue*>(plugin_value);
         base::string16 group_name;
         bool enabled;
         if (!plugin->GetBoolean("enabled", &enabled))
           enabled = true;
 
         base::FilePath::StringType path;
         // The plugin list constains all the plugin files in addition to the
         // plugin groups.
         if (plugin->GetString("path", &path)) {
           // Files have a path attribute, groups don't.
@@ skipping 158 matching lines @@
   }
 }
 
 void PluginPrefs::NotifyPluginStatusChanged() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_PLUGIN_ENABLE_STATUS_CHANGED,
       content::Source<Profile>(profile_),
       content::NotificationService::NoDetails());
 }