[NTP Snippets] FetchMore backend

components/ntp_snippets/content_suggestions_service.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/ntp_snippets/content_suggestions_service.h"
 
 #include <algorithm>
 #include <iterator>
 #include <set>
 #include <utility>
@@ skipping 178 matching lines @@
 void ContentSuggestionsService::RemoveObserver(Observer* observer) {
   observers_.RemoveObserver(observer);
 }
 
 void ContentSuggestionsService::RegisterProvider(
     std::unique_ptr<ContentSuggestionsProvider> provider) {
   DCHECK(state_ == State::ENABLED);
   providers_.push_back(std::move(provider));
 }
 
+void ContentSuggestionsService::FetchMore(const Category& category,
+                                          const FetchedMoreCallback& callback) {
+  auto providers_it = providers_by_category_.find(category);
+  if (providers_it == providers_by_category_.end())
+    return;
+
+  providers_it->second->FetchMore(category, callback);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Private methods
 
 void ContentSuggestionsService::OnNewSuggestions(
     ContentSuggestionsProvider* provider,
     Category category,
     std::vector<ContentSuggestion> suggestions) {
   // Providers shouldn't call this when they're in a non-available state.
   DCHECK(
       IsCategoryStatusInitOrAvailable(provider->GetCategoryStatus(category)));
@@ skipping 220 matching lines @@
 void ContentSuggestionsService::StoreDismissedCategoriesToPrefs() {
   base::ListValue list;
   for (const auto& category_provider_pair : dismissed_providers_by_category_) {
     list.AppendInteger(category_provider_pair.first.id());
   }
 
   pref_service_->Set(prefs::kDismissedCategories, list);
 }
 
 }  // namespace ntp_snippets