Use MediaGalleryPreferences directly in GalleryWatchStateTracker interface.

chrome/browser/media_galleries/media_galleries_preferences.h

Index: chrome/browser/media_galleries/media_galleries_preferences.h
diff --git a/chrome/browser/media_galleries/media_galleries_preferences.h b/chrome/browser/media_galleries/media_galleries_preferences.h
index 9e351b23f8239651b44a7b7d0901a07199f20a46..8069251ac4dd70c71f145db43d5f3a88fe1a5a67 100644
--- a/chrome/browser/media_galleries/media_galleries_preferences.h
+++ b/chrome/browser/media_galleries/media_galleries_preferences.h
@@ -115,14 +115,14 @@ class MediaGalleriesPreferences : public BrowserContextKeyedService,
                                   public RemovableStorageObserver {
  public:
   class GalleryChangeObserver {
-    public:
-     // |extension_id| specifies the extension affected by this change.
-     // It is empty if the gallery change affects all extensions.
-     virtual void OnGalleryChanged(MediaGalleriesPreferences* pref,
-                                   const std::string& extension_id) {}
-
-    protected:
-     virtual ~GalleryChangeObserver();
+   public:
+    // |extension_id| specifies the extension affected by this change.
+    // It is empty if the gallery change affects all extensions.
+    virtual void OnGalleryChanged(MediaGalleriesPreferences* pref,
+                                  const std::string& extension_id) {}
+
+   protected:
+    virtual ~GalleryChangeObserver();
   };
 
   explicit MediaGalleriesPreferences(Profile* profile);