Switch SupportsUserData uses to use unique_ptr.

components/offline_pages/core/downloads/download_ui_adapter.h

Index: components/offline_pages/core/downloads/download_ui_adapter.h
diff --git a/components/offline_pages/core/downloads/download_ui_adapter.h b/components/offline_pages/core/downloads/download_ui_adapter.h
index 2744f0b643826d72db24360edc43fb2e53821afd..9868fb009ca85bbd185ab5ef3218cf6e81c1f2be 100644
--- a/components/offline_pages/core/downloads/download_ui_adapter.h
+++ b/components/offline_pages/core/downloads/download_ui_adapter.h
@@ -83,8 +83,9 @@ class DownloadUIAdapter : public OfflinePageModel::Observer,
   ~DownloadUIAdapter() override;
 
   static DownloadUIAdapter* FromOfflinePageModel(OfflinePageModel* model);
-  static void AttachToOfflinePageModel(DownloadUIAdapter* adapter,
-                                       OfflinePageModel* model);
+  static void AttachToOfflinePageModel(
+      std::unique_ptr<DownloadUIAdapter> adapter,
+      OfflinePageModel* model);
 
   // This adapter is potentially shared by UI elements, each of which adds
   // itself as an observer.