Remove experimental code fro grouping notifications from the same source.

ui/message_center/views/message_popup_collection.cc

 // 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.
 
 #include "ui/message_center/views/message_popup_collection.h"
 
 #include <set>
 
 #include "base/bind.h"
 #include "base/i18n/rtl.h"
@@ skipping 122 matching lines @@
     const std::string& notification_id,
     int button_index) {
   message_center_->ClickOnNotificationButton(notification_id, button_index);
 }
 
 void MessagePopupCollection::ExpandNotification(
     const std::string& notification_id) {
   message_center_->ExpandNotification(notification_id);
 }
 
-void MessagePopupCollection::GroupBodyClicked(
-    const std::string& last_notification_id) {
-  // No group views in popup collection.
-  NOTREACHED();
-}
-
-// When clicked on the "N more" button, perform some reasonable action.
-// TODO(dimich): find out what the reasonable action could be.
-void MessagePopupCollection::ExpandGroup(const NotifierId& notifier_id) {
-  // No group views in popup collection.
-  NOTREACHED();
-}
-
-void MessagePopupCollection::RemoveGroup(const NotifierId& notifier_id) {
-  // No group views in popup collection.
-  NOTREACHED();
-}
-
 void MessagePopupCollection::MarkAllPopupsShown() {
   std::set<std::string> closed_ids = CloseAllWidgets();
   for (std::set<std::string>::iterator iter = closed_ids.begin();
        iter != closed_ids.end(); iter++) {
     message_center_->MarkSinglePopupAsShown(*iter, false);
   }
 }
 
 void MessagePopupCollection::UpdateWidgets() {
   NotificationList::PopupNotifications popups =
@@ skipping 459 matching lines @@
       views::Widget* widget = (*iter)->GetWidget();
       if (widget)
         return widget->GetWindowBoundsInScreen();
       break;
     }
   }
   return gfx::Rect();
 }
 
 }  // namespace message_center