Extract the view of control buttons on notification into a separated class

ui/message_center/views/message_view.cc

 // 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.
 
 #include "ui/message_center/views/message_view.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/models/simple_menu_model.h"
@@ skipping 217 matching lines @@
 void MessageView::OnSlideChanged() {}
 
 void MessageView::OnSlideOut() {
   controller_->RemoveNotification(notification_id_, true);  // By user.
 }
 
 void MessageView::OnCloseButtonPressed() {
   controller_->RemoveNotification(notification_id_, true);  // By user.
 }
 
+void MessageView::OnSettingsButtonPressed() {
+  controller_->ClickOnSettingsButton(notification_id_);
+}
+
 void MessageView::SetDrawBackgroundAsActive(bool active) {
   background_view_->background()->
       SetNativeControlColor(active ? kHoveredButtonBackgroundColor :
                                      kNotificationBackgroundColor);
   SchedulePaint();
 }
 
 }  // namespace message_center