Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/background/background_mode_manager.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 <algorithm>
 #include <string>
 #include <vector>
 
 #include "base/base_paths.h"
 #include "base/bind.h"
@@ skipping 266 matching lines @@
   return background_mode_data_.size();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 //  BackgroundModeManager, content::NotificationObserver overrides
 void BackgroundModeManager::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   switch (type) {
-    case chrome::NOTIFICATION_PREF_CHANGED:
-      DCHECK(*content::Details<std::string>(details).ptr() ==
-             prefs::kBackgroundModeEnabled);
-      OnBackgroundModeEnabledPrefChanged();
-      break;
     case chrome::NOTIFICATION_EXTENSIONS_READY:
       // Extensions are loaded, so we don't need to manually keep the browser
       // process alive any more when running in no-startup-window mode.
       EndKeepAliveForStartup();
       break;
 
     case chrome::NOTIFICATION_EXTENSION_LOADED: {
         Extension* extension = content::Details<Extension>(details).ptr();
         Profile* profile = content::Source<Profile>(source).ptr();
         if (BackgroundApplicationListModel::IsBackgroundApp(
@@ skipping 32 matching lines @@
            ++it) {
         it->second->applications_->RemoveObserver(this);
       }
       break;
     default:
       NOTREACHED();
       break;
   }
 }
 
+void BackgroundModeManager::OnPreferenceChanged(PrefServiceBase* service,
+                                                const std::string& pref_name) {
+  DCHECK(pref_name == prefs::kBackgroundModeEnabled);
+  OnBackgroundModeEnabledPrefChanged();
+}
+
 void BackgroundModeManager::OnBackgroundModeEnabledPrefChanged() {
   if (IsBackgroundModePrefEnabled())
     EnableBackgroundMode();
   else
     DisableBackgroundMode();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 //  BackgroundModeManager, BackgroundApplicationListModel::Observer overrides
 void BackgroundModeManager::OnApplicationDataChanged(
@@ skipping 417 matching lines @@
     }
   }
   return profile_it;
 }
 
 bool BackgroundModeManager::IsBackgroundModePrefEnabled() const {
   PrefService* service = g_browser_process->local_state();
   DCHECK(service);
   return service->GetBoolean(prefs::kBackgroundModeEnabled);
 }