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

components/offline_pages/core/prefetch/prefetch_service_impl.h

Index: components/offline_pages/core/prefetch/prefetch_service_impl.h
diff --git a/components/offline_pages/core/prefetch/prefetch_service_impl.h b/components/offline_pages/core/prefetch/prefetch_service_impl.h
index c476f13e90e0bbdf2a47530f71e58bcd3c6c14bb..05c7cabf1299a5e74ecab4dd7eb463d4e23e6e99 100644
--- a/components/offline_pages/core/prefetch/prefetch_service_impl.h
+++ b/components/offline_pages/core/prefetch/prefetch_service_impl.h
@@ -8,7 +8,13 @@
 #include <memory>
 
 #include "base/macros.h"
+#include "components/offline_pages/core/prefetch/prefetch_gcm_handler.h"
 #include "components/offline_pages/core/prefetch/prefetch_service.h"
+#include "components/offline_pages/core/prefetch/suggested_articles_observer.h"
+
+namespace ntp_snippets {
+class ContentSuggestionsService;
+}
 
 namespace offline_pages {
 
@@ -18,14 +24,20 @@ class PrefetchServiceImpl : public PrefetchService {
   ~PrefetchServiceImpl() override;
 
   // PrefetchService implementation:
+  void ObserveContentSuggestionsService(
+      ntp_snippets::ContentSuggestionsService* service) override;
+  void AddPrefetchGCMHandler(
+      std::unique_ptr<PrefetchGCMHandler> app_handler) override;
   PrefetchDispatcher* GetDispatcher() override;
 
   // KeyedService implementation:
   void Shutdown() override;
 
  private:
-  std::unique_ptr<PrefetchDispatcher> dispatcher_;
+  std::unique_ptr<SuggestedArticlesObserver> suggested_articles_observer_;
+  std::unique_ptr<PrefetchGCMHandler> gcm_handler_;
 
+  std::unique_ptr<PrefetchDispatcher> dispatcher_;
   DISALLOW_COPY_AND_ASSIGN(PrefetchServiceImpl);
 };