[NTP Snippets] FetchMore backend

components/ntp_snippets/content_suggestions_service.h

Index: components/ntp_snippets/content_suggestions_service.h
diff --git a/components/ntp_snippets/content_suggestions_service.h b/components/ntp_snippets/content_suggestions_service.h
index be34e7290c43a0f9f3db422e13111c16b0fee6c6..9b1b6664d6da5bd907a6ca7e6a037e8d47bc3dde 100644
--- a/components/ntp_snippets/content_suggestions_service.h
+++ b/components/ntp_snippets/content_suggestions_service.h
@@ -41,9 +41,12 @@ class ContentSuggestionsService : public KeyedService,
                                   public ContentSuggestionsProvider::Observer,
                                   public history::HistoryServiceObserver {
  public:
+  // TODO(treib): All these should probably be OnceCallback.

[Bernhard Bauer, 2016/10/28 16:26:00]

I didn't know about that. Neat! :)

[fhorschig, 2016/11/02 05:06:12]

Yeah, the logic was that these callbacks are responses to requests and a request
would not need more than one response.

   using ImageFetchedCallback = base::Callback<void(const gfx::Image&)>;
   using DismissedSuggestionsCallback = base::Callback<void(
       std::vector<ContentSuggestion> dismissed_suggestions)>;
+  using FetchedMoreCallback =
+      base::Callback<void(std::vector<ContentSuggestion> suggestions)>;
 
   class Observer {
    public:
@@ -135,6 +138,11 @@ class ContentSuggestionsService : public KeyedService,
   // Returns whether |category| is dismissed.
   bool IsCategoryDismissed(Category category) const;
 
+  // Fetches additional contents for the given |category|. If the fetch was
+  // completed, the given |callback| is called with the updated content.
+  // This includes new and old data.
+  void FetchMore(const Category& category, const FetchedMoreCallback& callback);
+
   // Observer accessors.
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);