Ntp: show AllDismissedItem when all sections have been dismissed.

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 987a9fb4accd0cf0d623b1b970cb0195a24be638..19e87fa27dd6ff663a87c155e8d2839e2d1d9643 100644
--- a/components/ntp_snippets/content_suggestions_service.h
+++ b/components/ntp_snippets/content_suggestions_service.h
@@ -125,6 +125,10 @@ class ContentSuggestionsService : public KeyedService,
   // This will not trigger an update through the observers.
   void DismissCategory(Category category);
 
+  // Restores all dismissed categories.
+  // This will not trigger an update through the observers.
+  void RestoreDismissedCategories();
+
   // Observer accessors.
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
@@ -242,6 +246,11 @@ class ContentSuggestionsService : public KeyedService,
   // |providers_by_category_|.
   std::vector<Category> categories_;
 
+  // All dismissed categories and their providers. These may be restored by
+  // RestoreDismissedCategories().
+  std::map<Category, ContentSuggestionsProvider*, Category::CompareByID>
+      dismissed_providers_by_category_;

[Marc Treib, 2016/10/07 11:40:13]

What's the status of persisting dismissals? Seems like this wouldn't really work
together - we can't persist the provider pointers.

Generally, I'm not too happy with Yet Another data structure storing
categories/providers here... can we just go over all providers instead and
re-register everything?

[Michael van Ouwerkerk, 2016/10/10 16:19:32]

Nicolas is working on persisting section dismissals. As discussed over chat,
keeping a separate data structure centralized in the service seems slightly
preferable to the alternatives of introducing an additional provider state, only
partially undoing what happens in RegisterCategoryIfRequired, or additional
provider / observer plumbing.

+
   // All current suggestions grouped by category. This contains an entry for
   // every category in |categories_| whose status is an available status. It may
   // contain an empty vector if the category is available but empty (or still