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

components/offline_pages/core/prefetch/prefetch_service_impl.cc

Index: components/offline_pages/core/prefetch/prefetch_service_impl.cc
diff --git a/components/offline_pages/core/prefetch/prefetch_service_impl.cc b/components/offline_pages/core/prefetch/prefetch_service_impl.cc
index 13f0eb3f40502706ad1a1fe7f2d6503c5f811f87..e7f49fdeccf5e70d813de856a226ee7c3a3cf6d8 100644
--- a/components/offline_pages/core/prefetch/prefetch_service_impl.cc
+++ b/components/offline_pages/core/prefetch/prefetch_service_impl.cc
@@ -3,12 +3,21 @@
 // found in the LICENSE file.
 
 #include "components/offline_pages/core/prefetch/prefetch_service_impl.h"
+#include "base/memory/ptr_util.h"
 
 namespace offline_pages {
 
-PrefetchServiceImpl::PrefetchServiceImpl() {}
+PrefetchServiceImpl::PrefetchServiceImpl(
+    std::unique_ptr<GCMAppHandler> gcm_app_handler)
+    : gcm_app_handler_(std::move(gcm_app_handler)) {}
 PrefetchServiceImpl::~PrefetchServiceImpl() = default;
 
+void PrefetchServiceImpl::ObserveContentSuggestionsService(
+    ntp_snippets::ContentSuggestionsService* service) {
+  suggested_articles_observer_ =
+      base::MakeUnique<SuggestedArticlesObserver>(service, this);
+}
+
 void PrefetchServiceImpl::AddCandidatePrefetchURLs(
     const std::vector<PrefetchURL>& url_suggestions) {
   NOTIMPLEMENTED();