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..8cc0d73db4e840da3f8c6975f5c83da31d93fb4a
--- /dev/null
+++ b/chrome/browser/extensions/api/media_galleries_private/media_gallery_extension_notification_observer.h
@@ -0,0 +1,45 @@
+// 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 "base/threading/thread_checker.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::NotificationDelegate implementation.

[Lei Zhang, 2012/12/15 01:11:54]

You meant to say NotificationObserver.

[kmadhusu, 2012/12/17 23:58:05]

oops. Fixed.

+  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_;
+
+  // Make sure all the member functions are called on the right thread.
+  base::ThreadChecker thread_checker_;

[Lei Zhang, 2012/12/15 01:11:54]

I think you are going overboard with ThreadCheckers. a)
NotificationObserver::Observe() isn't going to get called on any other thread.
If it does get called on the wrong thread, then Chrome will likely crash in
other horrible ways before it gets to your code. BUt let's say you really wanted
to check this. You still don't need a ThreadChecker. You can be more specific
and just check to see if you are on the UI thread.

[kmadhusu, 2012/12/17 23:58:05]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(MediaGalleryExtensionNotificationObserver);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_API_MEDIA_GALLERIES_PRIVATE_MEDIA_GALLERY_EXTENSION_NOTIFICATION_OBSERVER_H_