[Offline pages] Adapting OfflinePageDownloadBridge to DownloadUIAdapter

components/offline_pages/downloads/download_ui_adapter.cc

Index: components/offline_pages/downloads/download_ui_adapter.cc
diff --git a/components/offline_pages/downloads/download_ui_adapter.cc b/components/offline_pages/downloads/download_ui_adapter.cc
index efdc35242fdcca4e9254f423ad5480c24c0c9144..776fd8cd79b691e167cd48adfc895c7e9d622056 100644
--- a/components/offline_pages/downloads/download_ui_adapter.cc
+++ b/components/offline_pages/downloads/download_ui_adapter.cc
@@ -15,6 +15,10 @@
 
 namespace offline_pages {
 
+namespace {
+const char kDownloadUIAdapterKey[] = "download-ui-adapter";
+}
+
 DownloadUIAdapter::DownloadUIAdapter(OfflinePageModel* model)
     : model_(model),
       is_loaded_(false),
@@ -23,6 +27,18 @@ DownloadUIAdapter::DownloadUIAdapter(OfflinePageModel* model)
 
 DownloadUIAdapter::~DownloadUIAdapter() { }
 
+// static
+DownloadUIAdapter* DownloadUIAdapter::FromOfflinePageModel(
+    OfflinePageModel* offline_page_model) {
+  DownloadUIAdapter* adapter = static_cast<DownloadUIAdapter*>(
+      offline_page_model->GetUserData(kDownloadUIAdapterKey));
+  if (!adapter) {
+    adapter = new DownloadUIAdapter(offline_page_model);
+    offline_page_model->SetUserData(kDownloadUIAdapterKey, adapter);
+  }
+  return adapter;
+}
+
 void DownloadUIAdapter::AddObserver(Observer* observer) {
   DCHECK(observer);
   if (!observers_.might_have_observers())