Made notification center notifications collapsed and expandable.

ui/message_center/notification_change_observer.h

Index: ui/message_center/notification_change_observer.h
diff --git a/ui/message_center/notification_change_observer.h b/ui/message_center/notification_change_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..ff456854f93a8282a83eb3925f612e9ff4428e73
--- /dev/null
+++ b/ui/message_center/notification_change_observer.h
@@ -0,0 +1,35 @@
+// Copyright (c) 2013 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 UI_MESSAGE_CENTER_NOTIFICATION_CHANGE_OBSERVER_H_
+#define UI_MESSAGE_CENTER_NOTIFICATION_CHANGE_OBSERVER_H_
+
+#include <string>
+
+#include "ui/gfx/native_widget_types.h"
+
+namespace message_center {
+
+// For classes that need to handle or propagate notification changes.
+class MESSAGE_CENTER_EXPORT NotificationChangeObserver {
+ public:
+  virtual ~NotificationChangeObserver() {};
+
+  virtual void OnRemoveNotification(const std::string& id, bool by_user) {};
+  virtual void OnRemoveAllNotifications(bool by_user) {};
+
+  virtual void OnDisableNotificationsByExtension(const std::string& id) {};
+  virtual void OnDisableNotificationsByUrl(const std::string& id) {};
+
+  virtual void OnShowNotificationSettings(const std::string& id) {};
+  virtual void OnShowNotificationSettingsDialog(gfx::NativeView context) {};
+
+  virtual void OnExpanded(const std::string& id) {};
+  virtual void OnClicked(const std::string& id) {};
+  virtual void OnButtonClicked(const std::string& id, int button_index) {};
+};
+
+}  // namespace message_center
+
+#endif // UI_MESSAGE_CENTER_NOTIFICATION_CHANGE_OBSERVER_H_