Notifications: Add cross-platform UMA: ShowMessageCenter, ShowSettings.

ui/message_center/message_center_observer.h

 // 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_MESSAGE_CENTER_OBSERVER_H_
 #define UI_MESSAGE_CENTER_MESSAGE_CENTER_OBSERVER_H_
 
 #include <string>
 
 #include "ui/message_center/message_center_export.h"
+#include "ui/message_center/message_center_types.h"
 
 namespace message_center {
 
 // An observer class for the change of notifications in the MessageCenter.
 class MESSAGE_CENTER_EXPORT MessageCenterObserver {
  public:
   virtual ~MessageCenterObserver() {}
 
   // Called when the notification associated with |notification_id| is added
   // to the notification_list.
@@ skipping 14 matching lines @@
 
   // Called when a click event happens on a button indexed by |button_index|
   // of the notification associated with |notification_id|.
   virtual void OnNotificationButtonClicked(const std::string& notification_id,
                                            int button_index) {}
 
   // Called when the notification associated with |notification_id| is actually
   // displayed.
   virtual void OnNotificationDisplayed(const std::string& notification_id) {}
 
-  // Called when the notification list is no longer being displayed as a
-  // notification center.
-  virtual void OnNotificationCenterClosed() {}
+  // Called when the notification center is shown or hidden.
+  virtual void OnCenterVisibilityChanged(Visibility visibility) {}
 
   // Called whenever the quiet mode changes as a result of user action or when
   // quiet mode expires.
   virtual void OnQuietModeChanged(bool in_quiet_mode) {}
 };
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_MESSAGE_CENTER_OBSERVER_H_