Retrieve pinned flag directly from Notification class

ui/message_center/views/notification_view.cc

Index: ui/message_center/views/notification_view.cc
diff --git a/ui/message_center/views/notification_view.cc b/ui/message_center/views/notification_view.cc
index b12da677da574ba15370bd63502fe3fe41b6f349..1258273003f21b3a5817d84953633ff110145fd0 100644
--- a/ui/message_center/views/notification_view.cc
+++ b/ui/message_center/views/notification_view.cc
@@ -408,10 +408,6 @@ void NotificationView::RequestFocusOnCloseButton() {
     close_button_->RequestFocus();
 }
 
-bool NotificationView::IsPinned() const {
-  return !close_button_;
-}
-
 void NotificationView::CreateOrUpdateTitleView(
     const Notification& notification) {
   if (notification.title().empty()) {