[Offline Pages] Set up the initial prefetching service.

components/offline_pages/core/prefetch/prefetch_service_impl.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 "components/offline_pages/core/prefetch/prefetch_service_impl.h"
+
+namespace offline_pages {
+
+PrefetchServiceImpl::PrefetchServiceImpl() {}
+PrefetchServiceImpl::~PrefetchServiceImpl() = default;
+
+void PrefetchServiceImpl::OnNewURLSuggestions(
+    const std::vector<GURL> url_suggestions) {
+  NOTIMPLEMENTED();
+}
+void PrefetchServiceImpl::RemoveAllUnprocessedURLSuggestions() {
+  NOTIMPLEMENTED();
+}
+
+void PrefetchServiceImpl::Shutdown() {}
+
+}  // namespace offline_pages