Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/plugins/plugin_status_pref_setter.h

 // 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.
 
 #ifndef CHROME_BROWSER_PLUGINS_PLUGIN_STATUS_PREF_SETTER_H_
 #define CHROME_BROWSER_PLUGINS_PLUGIN_STATUS_PREF_SETTER_H_
 
 #include <vector>
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
 class PluginPrefs;
 class PrefService;
 class Profile;
 
 namespace webkit {
 struct WebPluginInfo;
 }
 
 // Helper class modeled after BooleanPrefMember to (asynchronously) update
 // preferences related to plugin enable status.
 // It should only be used from the UI thread. The client has to make sure that
 // the passed profile outlives this object.
 class PluginStatusPrefSetter : public content::NotificationObserver {
  public:
   PluginStatusPrefSetter();
   virtual ~PluginStatusPrefSetter();
 
   // Binds the preferences in the profile's PrefService, notifying |observer| if
   // any value changes.
   // This asynchronously calls the PluginService to get the list of installed
   // plug-ins.
-  void Init(Profile* profile,
-            content::NotificationObserver* observer);
+  void Init(Profile* profile, PrefObserver* observer);
 
   bool IsClearPluginLSODataEnabled() const {
     return clear_plugin_lso_data_enabled_.GetValue();
   }
 
   bool IsPepperFlashSettingsEnabled() const {
     return pepper_flash_settings_enabled_.GetValue();
   }
 
   // content::NotificationObserver methods:
@@ skipping 13 matching lines @@
 
   // Whether clearing LSO data is supported.
   BooleanPrefMember clear_plugin_lso_data_enabled_;
   // Whether we should show Pepper Flash-specific settings.
   BooleanPrefMember pepper_flash_settings_enabled_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginStatusPrefSetter);
 };
 
 #endif  // CHROME_BROWSER_PLUGINS_PLUGIN_STATUS_PREF_SETTER_H_