[Media Gallery] Add existing attached devices to the prefs in time for media galleries dialog.

chrome/browser/media_gallery/media_galleries_preferences_factory.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_MEDIA_GALLERY_MEDIA_GALLERIES_PREFERENCES_FACTORY_H_
 #define CHROME_BROWSER_MEDIA_GALLERY_MEDIA_GALLERIES_PREFERENCES_FACTORY_H_
 
 #include "base/basictypes.h"
 #include "base/memory/singleton.h"
 #include "chrome/browser/profiles/profile_keyed_service_factory.h"
 
 class Profile;
 
 namespace chrome {
 class MediaGalleriesPreferences;
 }
 
 // Singleton that owns all MediaGalleriesPreferences and associates them with
 // Profiles.
 class MediaGalleriesPreferencesFactory : public ProfileKeyedServiceFactory {
  public:
+  // Use MediaFileSystemRegistry::GetPreferences() to get
+  // MediaGalleriesPreferences.
   static chrome::MediaGalleriesPreferences* GetForProfile(Profile* profile);
 
   static MediaGalleriesPreferencesFactory* GetInstance();
 
  private:
   friend struct DefaultSingletonTraits<MediaGalleriesPreferencesFactory>;
 
   MediaGalleriesPreferencesFactory();
   virtual ~MediaGalleriesPreferencesFactory();
 
   // ProfileKeyedServiceFactory:
   virtual ProfileKeyedService* BuildServiceInstanceFor(
       Profile* profile) const OVERRIDE;
   virtual void RegisterUserPrefs(PrefService* prefs) OVERRIDE;
   virtual bool ServiceRedirectedInIncognito() const OVERRIDE;
 
   DISALLOW_COPY_AND_ASSIGN(MediaGalleriesPreferencesFactory);
 };
 
 #endif  // CHROME_BROWSER_MEDIA_GALLERY_MEDIA_GALLERIES_PREFERENCES_FACTORY_H_