Remove the last usages of PrefObserver outside of Prefs.

chrome/browser/ui/webui/plugins_ui.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/ui/webui/plugins_ui.h"
 
 #include <algorithm>
 #include <string>
 #include <vector>
 
@@ skipping 175 matching lines @@
 };
 
 PluginsDOMHandler::PluginsDOMHandler()
     : ALLOW_THIS_IN_INITIALIZER_LIST(weak_ptr_factory_(this)) {
 }
 
 void PluginsDOMHandler::RegisterMessages() {
   Profile* profile = Profile::FromWebUI(web_ui());
 
   PrefService* prefs = profile->GetPrefs();
-  show_details_.Init(prefs::kPluginsShowDetails, prefs, NULL);
+  show_details_.Init(prefs::kPluginsShowDetails, prefs);
 
   registrar_.Add(this,
                  chrome::NOTIFICATION_PLUGIN_ENABLE_STATUS_CHANGED,
                  content::Source<Profile>(profile));
 
   web_ui()->RegisterMessageCallback("requestPluginsData",
       base::Bind(&PluginsDOMHandler::HandleRequestPluginsData,
                  base::Unretained(this)));
   web_ui()->RegisterMessageCallback("enablePlugin",
       base::Bind(&PluginsDOMHandler::HandleEnablePluginMessage,
@@ skipping 284 matching lines @@
 }
 
 // static
 void PluginsUI::RegisterUserPrefs(PrefService* prefs) {
   prefs->RegisterBooleanPref(prefs::kPluginsShowDetails,
                              false,
                              PrefService::UNSYNCABLE_PREF);
   prefs->RegisterDictionaryPref(prefs::kContentSettingsPluginWhitelist,
                                 PrefService::SYNCABLE_PREF);
 }