[Offline pages] Adapting OfflinePageDownloadBridge to DownloadUIAdapter

components/offline_pages/downloads/download_ui_adapter.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/offline_pages/downloads/download_ui_adapter.h"
 
 #include "base/bind.h"
 #include "base/guid.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/offline_pages/client_namespace_constants.h"
 #include "components/offline_pages/downloads/download_ui_item.h"
 #include "components/offline_pages/offline_page_model.h"
 
 namespace offline_pages {
 
+namespace {
+const char kDownloadUIAdapterKey[] = "download-ui-adapter";
+}
+
 DownloadUIAdapter::DownloadUIAdapter(OfflinePageModel* model)
     : model_(model),
       is_loaded_(false),
       weak_ptr_factory_(this) {
 }
 
 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())
     LoadCache();
   observers_.AddObserver(observer);
   // If the items are already loaded, post the notification right away.
   // Don't just invoke it from here to avoid reentrancy in the client.
   if (is_loaded_) {
     base::ThreadTaskRunnerHandle::Get()->PostTask(
         FROM_HERE, base::Bind(&DownloadUIAdapter::NotifyItemsLoaded,
@@ skipping 101 matching lines @@
   }
 }
 
 bool DownloadUIAdapter::IsVisibleInUI(const OfflinePageItem& page) {
   // TODO(dimich): set up the right filter here.
   return page.client_id.name_space == kAsyncNamespace &&
          base::IsValidGUID(page.client_id.id);
 }
 
 }  // namespace offline_pages