Remove experimental code fro grouping notifications from the same source.

ui/message_center/views/toast_contents_view.cc

Index: ui/message_center/views/toast_contents_view.cc
diff --git a/ui/message_center/views/toast_contents_view.cc b/ui/message_center/views/toast_contents_view.cc
index a1bc249e7fa1fde47f63b16204f0b63fbabc72ce..0b3ff313f0a0044df96229da2a5b31f183925eb1 100644
--- a/ui/message_center/views/toast_contents_view.cc
+++ b/ui/message_center/views/toast_contents_view.cc
@@ -329,24 +329,6 @@ void ToastContentsView::ExpandNotification(
     collection_->ExpandNotification(notification_id);
 }
 
-void ToastContentsView::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 ToastContentsView::ExpandGroup(const NotifierId& notifier_id) {
-  // No group views in popup collection.
-  NOTREACHED();
-}
-
-void ToastContentsView::RemoveGroup(const NotifierId& notifier_id) {
-  // No group views in popup collection.
-  NOTREACHED();
-}
-
 void ToastContentsView::CreateWidget(gfx::NativeView parent) {
   views::Widget::InitParams params(views::Widget::InitParams::TYPE_POPUP);
   params.keep_on_top = true;