Adjust behavior of control buttons of notifications.

ui/message_center/views/custom_notification_view.cc

Index: ui/message_center/views/custom_notification_view.cc
diff --git a/ui/message_center/views/custom_notification_view.cc b/ui/message_center/views/custom_notification_view.cc
index 6896796d841bd45cc8fba708e392a779bd712895..e3787fef5b4e8ba00f4391daa15d929aa47dc759 100644
--- a/ui/message_center/views/custom_notification_view.cc
+++ b/ui/message_center/views/custom_notification_view.cc
@@ -78,6 +78,11 @@ bool CustomNotificationView::IsPinned() const {
   return contents_view_delegate_->IsPinned();
 }
 
+void CustomNotificationView::UpdateControlButtonsVisibility() {
+  if (contents_view_delegate_)
+    contents_view_delegate_->UpdateControlButtonsVisibility();
+}
+
 gfx::Size CustomNotificationView::GetPreferredSize() const {
   const gfx::Insets insets = GetInsets();
   const int contents_width = kNotificationWidth - insets.width();