Add ContentSuggestionsService

components/ntp_snippets/ntp_snippets_service.h

Index: components/ntp_snippets/ntp_snippets_service.h
diff --git a/components/ntp_snippets/ntp_snippets_service.h b/components/ntp_snippets/ntp_snippets_service.h
index 57542c118dacd18af251ddc534d2f28aab0503fd..18a45de9b8e2ad32513c17a6af21f9b5840dd5c7 100644
--- a/components/ntp_snippets/ntp_snippets_service.h
+++ b/components/ntp_snippets/ntp_snippets_service.h
@@ -12,6 +12,7 @@
 #include <string>
 #include <vector>
 
+#include "base/callback_forward.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/observer_list.h"
@@ -329,8 +330,10 @@ class NTPSnippetsServiceObserver {
  public:
   // Sent every time the service loads a new set of data.
   virtual void NTPSnippetsServiceLoaded() = 0;
+
   // Sent when the service is shutting down.
   virtual void NTPSnippetsServiceShutdown() = 0;
+
   // Sent when the service has been disabled. Can be from explicit user action
   // or because a requirement (e.g. History Sync) is not fulfilled anymore.
   virtual void NTPSnippetsServiceDisabled() = 0;