Hide popup custom notifications on non-primary displays

ui/message_center/views/popup_alignment_delegate.h

Index: ui/message_center/views/popup_alignment_delegate.h
diff --git a/ui/message_center/views/popup_alignment_delegate.h b/ui/message_center/views/popup_alignment_delegate.h
index 6be86cbd860bd725159adfd1223a9e8b04d4242f..48787456927626bd215a5af4aa7d55dc06117670 100644
--- a/ui/message_center/views/popup_alignment_delegate.h
+++ b/ui/message_center/views/popup_alignment_delegate.h
@@ -56,6 +56,10 @@ class MESSAGE_CENTER_EXPORT PopupAlignmentDelegate {
       views::Widget* widget,
       views::Widget::InitParams* init_params) = 0;
 
+  // Returns true if the display which notifications show on is the primary
+  // display.
+  virtual bool IsPrimaryDisplayForNotification() const = 0;
+
  protected:
   virtual ~PopupAlignmentDelegate();