Hide popup custom notifications on non-primary displays

ui/message_center/views/desktop_popup_alignment_delegate.cc

Index: ui/message_center/views/desktop_popup_alignment_delegate.cc
diff --git a/ui/message_center/views/desktop_popup_alignment_delegate.cc b/ui/message_center/views/desktop_popup_alignment_delegate.cc
index d6e7ff8f131df535bb73f9c5329da4ce29663430..f57d23ad449ff3073a47ea76a368d06da8b523fa 100644
--- a/ui/message_center/views/desktop_popup_alignment_delegate.cc
+++ b/ui/message_center/views/desktop_popup_alignment_delegate.cc
@@ -89,6 +89,10 @@ void DesktopPopupAlignmentDelegate::ConfigureWidgetInitParamsForContainer(
   // Do nothing, which will use the default container.
 }
 
+bool DesktopPopupAlignmentDelegate::IsPrimaryDisplayForNotification() const {
+  return true;
+}
+
 // Anytime the display configuration changes, we need to recompute the alignment
 // on the primary display. But, we get different events on different platforms.
 // On Windows, for example, when switching from a laptop display to an external