[arc notifications] Inspect pinned flag directly for IsPinned().

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 cdb2c7da5a0f59fe3ac3440d5c51865e94e37ee3..71b8777a499c0049acdcf1185b6ab2d157d2d7ba 100644
--- a/ui/arc/notification/arc_custom_notification_view.cc
+++ b/ui/arc/notification/arc_custom_notification_view.cc
@@ -169,7 +169,7 @@ class ArcCustomNotificationView::ContentViewDelegate
   }
 
   bool IsPinned() const override {
-    return owner_->floating_close_button_ == nullptr;
+    return owner_->item_->pinned();
   }
 
  private: