[Offline Pages] Set up the initial prefetching service.

components/offline_pages/content/prefetch_service_factory.h

Index: components/offline_pages/content/prefetch_service_factory.h
diff --git a/components/offline_pages/content/prefetch_service_factory.h b/components/offline_pages/content/prefetch_service_factory.h
new file mode 100644
index 0000000000000000000000000000000000000000..c7f4fb16696cc9fc71368d0547c385f894e01bcc
--- /dev/null
+++ b/components/offline_pages/content/prefetch_service_factory.h
@@ -0,0 +1,43 @@
+// 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.
+
+#ifndef COMPONENTS_OFFLINE_PAGES_CONTENT_PREFETCH_SERVICE_FACTORY_H_
+#define COMPONENTS_OFFLINE_PAGES_CONTENT_PREFETCH_SERVICE_FACTORY_H_
+
+#include "base/macros.h"
+#include "components/keyed_service/content/browser_context_keyed_service_factory.h"
+
+namespace base {
+template <typename T>
+struct DefaultSingletonTraits;
+}  // namespace base
+
+namespace offline_pages {
+
+class PrefetchService;
+
+// A factory to create one PrefetchServiceImpl per browser context. Prefetching
+// Offline Pages is not supported in incognito, so this class uses default
+// implementation of |GetBrowserContextToUse|.
+class PrefetchServiceFactory : public BrowserContextKeyedServiceFactory {
+ public:
+  static PrefetchServiceFactory* GetInstance();
+  static PrefetchService* GetForBrowserContext(
+      content::BrowserContext* context);
+
+ private:
+  friend struct base::DefaultSingletonTraits<PrefetchServiceFactory>;
+
+  PrefetchServiceFactory();
+  ~PrefetchServiceFactory() override {}
+
+  KeyedService* BuildServiceInstanceFor(
+      content::BrowserContext* context) const override;
+
+  DISALLOW_COPY_AND_ASSIGN(PrefetchServiceFactory);
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_CONTENT_PREFETCH_SERVICE_FACTORY_H_