[Offline Pages] Set up the initial prefetching service.

chrome/browser/android/offline_pages/prefetch_service_factory.cc

+// Copyright 2017 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 "chrome/browser/android/offline_pages/prefetch_service_factory.h"
+
+#include <utility>
+
+#include "base/files/file_path.h"
+#include "base/memory/singleton.h"
+#include "base/sequenced_task_runner.h"
+#include "base/threading/sequenced_worker_pool.h"
+#include "chrome/browser/profiles/incognito_helpers.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/common/chrome_constants.h"
+#include "components/keyed_service/content/browser_context_dependency_manager.h"
+#include "components/offline_pages/core/offline_page_metadata_store_sql.h"
+#include "components/offline_pages/core/prefetch/prefetch_service_impl.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace offline_pages {
+
+PrefetchServiceFactory::PrefetchServiceFactory()
+    : BrowserContextKeyedServiceFactory(
+          "OfflinePagePrefetchService",
+          BrowserContextDependencyManager::GetInstance()) {}
+
+// static
+PrefetchServiceFactory* PrefetchServiceFactory::GetInstance() {
+  return base::Singleton<PrefetchServiceFactory>::get();
+}
+
+// static
+PrefetchService* PrefetchServiceFactory::GetForBrowserContext(
+    content::BrowserContext* context) {
+  return static_cast<PrefetchService*>(
+      GetInstance()->GetServiceForBrowserContext(context, true));
+}
+
+KeyedService* PrefetchServiceFactory::BuildServiceInstanceFor(
+    content::BrowserContext* context) const {
+  scoped_refptr<base::SequencedTaskRunner> background_task_runner =

[Dmitry Titov, 2017/04/11 01:17:13]

this seems not used...

[dewittj, 2017/04/11 21:25:48]

Done.

+      content::BrowserThread::GetBlockingPool()->GetSequencedTaskRunner(
+          content::BrowserThread::GetBlockingPool()->GetSequenceToken());
+  return new PrefetchServiceImpl();
+}
+
+}  // namespace offline_pages