Retrieve pinned flag directly from Notification class

ui/arc/notification/arc_custom_notification_view.cc

Index: ui/arc/notification/arc_custom_notification_view.cc
diff --git a/ui/arc/notification/arc_custom_notification_view.cc b/ui/arc/notification/arc_custom_notification_view.cc
index 0c8c2ea404313552bb7e8ac750756954ab1e9fad..e63acd15d3d3aebcc2b75d58e21b81278b439897 100644
--- a/ui/arc/notification/arc_custom_notification_view.cc
+++ b/ui/arc/notification/arc_custom_notification_view.cc
@@ -190,12 +190,6 @@ class ArcCustomNotificationView::ContentViewDelegate
     owner_->UpdateControlButtonsVisibility();
   }
 
-  bool IsPinned() const override {
-    if (!owner_->item_)
-      return false;
-    return owner_->item_->pinned();
-  }
-
   void UpdateControlButtonsVisibility() override {
     owner_->UpdateControlButtonsVisibility();
   }