FetchMore functionality backend

components/ntp_snippets/content_suggestions_provider.h

Index: components/ntp_snippets/content_suggestions_provider.h
diff --git a/components/ntp_snippets/content_suggestions_provider.h b/components/ntp_snippets/content_suggestions_provider.h
index f6741356d66e6cfc0a3773c83c8afe25a6d63d83..0eca4e8c0ba44ac9efbc6c5679caa993e638f1bb 100644
--- a/components/ntp_snippets/content_suggestions_provider.h
+++ b/components/ntp_snippets/content_suggestions_provider.h
@@ -31,6 +31,8 @@ class ContentSuggestionsProvider {
   using ImageFetchedCallback = base::Callback<void(const gfx::Image&)>;
   using DismissedSuggestionsCallback = base::Callback<void(
       std::vector<ContentSuggestion> dismissed_suggestions)>;
+  using FetchedMoreCallback =

[vitaliii, 2016/11/01 23:29:57]

nit: FetchMoreCallback or MultipleContentSuggestionCallback

[fhorschig, 2016/11/02 05:05:27]

Renamed (but shorter) in CL 2466863003.

+      base::Callback<void(std::vector<ContentSuggestion> suggestions)>;
 
   // The observer of a provider is notified when new data is available.
   class Observer {
@@ -100,6 +102,12 @@ class ContentSuggestionsProvider {
   virtual void FetchSuggestionImage(const ContentSuggestion::ID& suggestion_id,
                                     const ImageFetchedCallback& callback) = 0;
 
+  // A user-triggered request to fetch more content for the given category.

[vitaliii, 2016/11/01 23:29:57]

"User-triggered" seems to be not relevant here, the comment should tell what the
function does, e.g. "Fetches new content suggestions..."

[fhorschig, 2016/11/02 05:05:27]

Done. (in CL 2466863003)

+  // Provides only suggestions that have not been provided. The given |callback|

[vitaliii, 2016/11/01 23:29:57]

This sentence looks contradicting to the next line. "Provides" is ambiguous to
me in this context.

[fhorschig, 2016/11/02 05:05:27]

Done. (in CL 2466863003)

+  // is called with these suggestion, along with all existing suggestions.

[vitaliii, 2016/11/01 23:29:57]

s/suggestion/suggestionS

[fhorschig, 2016/11/02 05:05:27]

Done. (in CL 2466863003)

+  virtual void FetchMore(const Category& category,
+                         const FetchedMoreCallback& callback) = 0;
+
   // Removes history from the specified time range where the URL matches the
   // |filter|. The data removed depends on the provider. Note that the
   // data outside the time range may be deleted, for example suggestions, which