Stop notifications from being clipped on resize.

ui/message_center/views/message_center_view.h

Index: ui/message_center/views/message_center_view.h
diff --git a/ui/message_center/views/message_center_view.h b/ui/message_center/views/message_center_view.h
index bd923fa531b1879c04c4a9d9ddb7614d94e16e90..da206b0ca08b845ee7c4163d1425c182e1774ff0 100644
--- a/ui/message_center/views/message_center_view.h
+++ b/ui/message_center/views/message_center_view.h
@@ -62,6 +62,10 @@ class MESSAGE_CENTER_EXPORT MessageCenterView
   void SetIsClosing(bool is_closing);
 
  protected:
+  // Potentially sets the reposition target, and then returns whether or not it
+  // was was set.
+  virtual bool SetRepositionTarget();
+
   // Overridden from views::View:
   void Layout() override;
   gfx::Size GetPreferredSize() const override;