[Offline Pages] Add a GCMAppHandler for offline page prefetch.

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;
@@ skipping 14 matching lines @@
 
 void PrefetchServiceImpl::BeginBackgroundTask(
     std::unique_ptr<ScopedBackgroundTask> task) {
   NOTIMPLEMENTED();
 }
 
 void PrefetchServiceImpl::StopBackgroundTask(ScopedBackgroundTask* task) {
   NOTIMPLEMENTED();
 }
 
+void PrefetchServiceImpl::ShutdownHandler() {}
+
+void PrefetchServiceImpl::OnStoreReset() {}
+
+void PrefetchServiceImpl::OnMessage(const std::string& app_id,
+                                    const gcm::IncomingMessage& message) {
+  DVLOG(1) << "PrefetchServiceImpl " << __func__ << ":" << message.raw_data;
+}
+
+void PrefetchServiceImpl::OnMessagesDeleted(const std::string& app_id) {
+  NOTIMPLEMENTED();
+}
+
+void PrefetchServiceImpl::OnSendError(
+    const std::string& app_id,
+    const gcm::GCMClient::SendErrorDetails& send_error_details) {
+  // We should never get here, since we are not sending GCM upstream.
+  NOTREACHED();
+}
+
+void PrefetchServiceImpl::OnSendAcknowledged(const std::string& app_id,
+                                             const std::string& message_id) {
+  // We should never get here, since we are not sending GCM upstream.
+  NOTREACHED();
+}
+
 void PrefetchServiceImpl::Shutdown() {}
 
 }  // namespace offline_pages