Implement mediaGalleriesPrivate api to notify extensions about gallery changed events.

chrome/browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.h

Index: chrome/browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.h
diff --git a/chrome/browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.h b/chrome/browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..915c8ea205ebfaa1445fce4b2026b4a526090c82
--- /dev/null
+++ b/chrome/browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.h
@@ -0,0 +1,41 @@
+// 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.
+
+// This class observes media gallery extension notification events. This
+// class object is created, destructed and operated on the UI thread.
+
+#ifndef CHROME_BROWSER_EXTENSIONS_API_MEDIA_GALLERIES_PRIVATE_MEDIA_GALLERY_EXTENSION_NOTIFICATION_OBSERVER_H_
+#define CHROME_BROWSER_EXTENSIONS_API_MEDIA_GALLERIES_PRIVATE_MEDIA_GALLERY_EXTENSION_NOTIFICATION_OBSERVER_H_
+
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+
+class Profile;
+
+namespace extensions {
+
+class MediaGalleryExtensionNotificationObserver
+    : public content::NotificationObserver {
+ public:
+  explicit MediaGalleryExtensionNotificationObserver(Profile* profile);
+  virtual ~MediaGalleryExtensionNotificationObserver();
+
+ private:
+  // content::NotificationObserver implementation.
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+  // Current profile.
+  Profile* profile_;
+
+  // Used to listen for NOTIFICATION_EXTENSION_UNLOADED and
+  // NOTIFICATION_EXTENSION_HOST_DESTROYED events.
+  content::NotificationRegistrar registrar_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaGalleryExtensionNotificationObserver);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_API_MEDIA_GALLERIES_PRIVATE_MEDIA_GALLERY_EXTENSION_NOTIFICATION_OBSERVER_H_