[Offline pages] Adapting OfflinePageDownloadBridge to DownloadUIAdapter

components/offline_pages/downloads/download_ui_adapter.h

Index: components/offline_pages/downloads/download_ui_adapter.h
diff --git a/components/offline_pages/downloads/download_ui_adapter.h b/components/offline_pages/downloads/download_ui_adapter.h
index 9363a946bff488b015186cfcca5e04e467a1cf0b..d96f11d7da757836ac0aee7a2cfc360b2a58b5e3 100644
--- a/components/offline_pages/downloads/download_ui_adapter.h
+++ b/components/offline_pages/downloads/download_ui_adapter.h
@@ -10,6 +10,7 @@
 #include <string>
 
 #include "base/observer_list.h"
+#include "base/supports_user_data.h"
 #include "components/offline_pages/downloads/download_ui_item.h"
 #include "components/offline_pages/offline_page_model.h"
 #include "components/offline_pages/offline_page_types.h"
@@ -26,7 +27,8 @@ typedef
 // UI components if needed. It manages the cache of DownloadUIItems, so after
 // initial load the UI components can synchronously pull the whoel list or any
 // item by its guid.
-class DownloadUIAdapter : public OfflinePageModel::Observer {
+class DownloadUIAdapter : public OfflinePageModel::Observer,
+                          public base::SupportsUserData::Data {
  public:
   // Observer, normally implemented by UI or a Bridge.
   class Observer {
@@ -54,6 +56,9 @@ class DownloadUIAdapter : public OfflinePageModel::Observer {
   explicit DownloadUIAdapter(OfflinePageModel* model);
   ~DownloadUIAdapter() override;
 
+  static DownloadUIAdapter* FromOfflinePageModel(
+      OfflinePageModel* offline_page_model);
+
   // This adapter is potentially shared by UI elements, each of which adds
   // itself as an observer.
   // When the last observer si removed, cached list of items is destroyed and
@@ -99,4 +104,4 @@ class DownloadUIAdapter : public OfflinePageModel::Observer {
 
 }  // namespace offline_pages
 
-#endif  // COMPONENTS_OFFLINE_PAGE_DOWNLOADS_DOWNLOAD_UI_ADAPTER_H_
+#endif  // COMPONENTS_OFFLINE_PAGE_DOWNLOADS_DOWNLOAD_UI_ADAPTER_H_