Show no-notification message in the bottom label of message center

ui/message_center/views/message_center_button_bar.h

Index: ui/message_center/views/message_center_button_bar.h
diff --git a/ui/message_center/views/message_center_button_bar.h b/ui/message_center/views/message_center_button_bar.h
index e7932abd1b5463d0344a9938994ae8810f5cc477..3d7420549eee77fc218a8be1c531da18b4288e9a 100644
--- a/ui/message_center/views/message_center_button_bar.h
+++ b/ui/message_center/views/message_center_button_bar.h
@@ -49,6 +49,9 @@ class MessageCenterButtonBar : public views::View,
   // Sometimes we shouldn't see the back arrow (not in settings).
   void SetBackArrowVisible(bool visible);
 
+  // Update the label of the title.
+  void SetTitle(const base::string16& title);
+
  private:
   // Updates the layout manager which can have differing configuration
   // depending on the visibility of different parts of the button bar.