Ntp: show AllDismissedItem when all sections have been dismissed.

components/ntp_snippets/content_suggestions_service.cc

Index: components/ntp_snippets/content_suggestions_service.cc
diff --git a/components/ntp_snippets/content_suggestions_service.cc b/components/ntp_snippets/content_suggestions_service.cc
index f52a9809d09dcae42dbad4cd9a62ff9598870423..8b1bdc15eae83a3180fece814448f8805d01484f 100644
--- a/components/ntp_snippets/content_suggestions_service.cc
+++ b/components/ntp_snippets/content_suggestions_service.cc
@@ -150,11 +150,24 @@ void ContentSuggestionsService::DismissCategory(Category category) {
   if (providers_it == providers_by_category_.end())
     return;
 
+  suggestions_by_category_[category].clear();
+  dismissed_providers_by_category_[providers_it->first] = providers_it->second;
   providers_by_category_.erase(providers_it);
   categories_.erase(
       std::find(categories_.begin(), categories_.end(), category));
 }
 
+void ContentSuggestionsService::RestoreDismissedCategories() {
+  // Make a copy as the original will be modified during iteration.
+  auto dismissed_providers_by_category_copy = dismissed_providers_by_category_;
+  for (const auto& category_provider_pair :
+       dismissed_providers_by_category_copy) {
+    RegisterCategoryIfRequired(category_provider_pair.second,
+                               category_provider_pair.first);
+  }
+  DCHECK(dismissed_providers_by_category_.empty());
+}
+
 void ContentSuggestionsService::AddObserver(Observer* observer) {
   observers_.AddObserver(observer);
 }
@@ -274,6 +287,12 @@ bool ContentSuggestionsService::RegisterCategoryIfRequired(
     return false;
   }
 
+  auto dismissed_it = dismissed_providers_by_category_.find(category);
+  if (dismissed_it != dismissed_providers_by_category_.end()) {
+    DCHECK_EQ(dismissed_it->second, provider);
+    dismissed_providers_by_category_.erase(dismissed_it);
+  }
+
   providers_by_category_[category] = provider;
   categories_.push_back(category);
   SortCategories();