Delete MessageViews cleared by "Clear All" after animation.

ui/message_center/views/message_list_view.cc

Index: ui/message_center/views/message_list_view.cc
diff --git a/ui/message_center/views/message_list_view.cc b/ui/message_center/views/message_list_view.cc
index 653b3f825a6fea4004c1f07a230e1f38bc848424..51139d22fe9c870930d30a9a12df78ddedf28eb7 100644
--- a/ui/message_center/views/message_list_view.cc
+++ b/ui/message_center/views/message_list_view.cc
@@ -560,6 +560,9 @@ void MessageListView::AnimateClearingOneNotification() {
   new_bounds.set_x(new_bounds.right() + kMarginBetweenItems);
   animator_.AnimateViewTo(child, new_bounds);
 
+  // Deleting the child after animation.
+  deleted_when_done_.insert(child);
+
   // Schedule to start sliding out next notification after a short delay.
   if (!clearing_all_views_.empty()) {
     base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(