[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"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "components/offline_pages/core/prefetch/prefetch_dispatcher_impl.h"
 
 namespace offline_pages {
 
 PrefetchServiceImpl::PrefetchServiceImpl()
     : dispatcher_(base::MakeUnique<PrefetchDispatcherImpl>()) {}
 
 PrefetchServiceImpl::~PrefetchServiceImpl() = default;
 
+void PrefetchServiceImpl::ObserveContentSuggestionsService(
+    ntp_snippets::ContentSuggestionsService* service) {

[fgorski, 2017/05/30 18:20:05]

CHECK or DCHECK to ensure we are not passing in the nullptr in production?

[dewittj, 2017/05/30 21:09:18]

Not going to change this code in this patch.

+  suggested_articles_observer_ =
+      base::MakeUnique<SuggestedArticlesObserver>(service, this);
+}
+
+void PrefetchServiceImpl::AddPrefetchGCMHandler(
+    std::unique_ptr<PrefetchGCMHandler> app_handler) {
+  gcm_handler_ = std::move(app_handler);
+}
+
 PrefetchDispatcher* PrefetchServiceImpl::GetDispatcher() {
   return dispatcher_.get();
-};
+}
 
 void PrefetchServiceImpl::Shutdown() {}
 
 }  // namespace offline_pages