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

ui/message_center/views/message_center_button_bar.cc

Index: ui/message_center/views/message_center_button_bar.cc
diff --git a/ui/message_center/views/message_center_button_bar.cc b/ui/message_center/views/message_center_button_bar.cc
index a92a5c4b002e249d6ef976dfafb08372606c4f87..47613da4f3167ddb158b6d6aa50957e1b4df972f 100644
--- a/ui/message_center/views/message_center_button_bar.cc
+++ b/ui/message_center/views/message_center_button_bar.cc
@@ -278,6 +278,10 @@ void MessageCenterButtonBar::SetBackArrowVisible(bool visible) {
   Layout();
 }
 
+void MessageCenterButtonBar::SetTitle(const base::string16& title) {
+  notification_label_->SetText(title);
+}
+
 void MessageCenterButtonBar::ChildVisibilityChanged(views::View* child) {
   InvalidateLayout();
 }