[NTP::Push] Adding BreakingNewsSuggestionsProvider

components/ntp_snippets/breaking_news/content_suggestions_gcm_app_handler.h

Index: components/ntp_snippets/breaking_news/content_suggestions_gcm_app_handler.h
diff --git a/components/ntp_snippets/breaking_news/content_suggestions_gcm_app_handler.h b/components/ntp_snippets/breaking_news/content_suggestions_gcm_app_handler.h
index 6636757c8a373580b9428a39a7a2156f18459934..05041bb6accf9bd31cb9999e0bf1e2a056ae5be9 100644
--- a/components/ntp_snippets/breaking_news/content_suggestions_gcm_app_handler.h
+++ b/components/ntp_snippets/breaking_news/content_suggestions_gcm_app_handler.h
@@ -29,6 +29,9 @@ namespace ntp_snippets {
 // be called upon received push content suggestions.
 class ContentSuggestionsGCMAppHandler : public gcm::GCMAppHandler {
  public:
+  // TODO(mamir): Check if a better paramater datatype makes more sense.
+  using OnNewContentCallback = base::Callback<void(const std::string& content)>;
+
   ContentSuggestionsGCMAppHandler(
       gcm::GCMDriver* gcm_driver,
       instance_id::InstanceIDDriver* instance_id_driver,
@@ -40,7 +43,7 @@ class ContentSuggestionsGCMAppHandler : public gcm::GCMAppHandler {
 
   // Subscribe to the GCM service if necessary and start listening for pushed
   // content suggestions. Must not be called if already listening.
-  void StartListening();
+  void StartListening(OnNewContentCallback on_new_content_callback);
 
   // Remove the handler, and stop listening for incoming GCM messages. Any
   // further pushed content suggestions will be ignored. Must be called while
@@ -76,6 +79,10 @@ class ContentSuggestionsGCMAppHandler : public gcm::GCMAppHandler {
   const std::unique_ptr<SubscriptionManager> subscription_manager_;
   base::WeakPtrFactory<ContentSuggestionsGCMAppHandler> weak_factory_;
 
+  // Called after everytime a new message is received in OnMessage() to notify
+  // the content provider.
+  OnNewContentCallback on_new_content_callback_;
+
   DISALLOW_COPY_AND_ASSIGN(ContentSuggestionsGCMAppHandler);
 };
 }  // namespace ntp_snippets