[Content suggestions] Add a function to the service API to fetch favicons

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 107 matching lines @@
     LOG(WARNING) << "Requested image for suggestion " << suggestion_id
                  << " for unavailable category " << suggestion_id.category();
     base::ThreadTaskRunnerHandle::Get()->PostTask(
         FROM_HERE, base::Bind(callback, gfx::Image()));
     return;
   }
   providers_by_category_[suggestion_id.category()]->FetchSuggestionImage(
       suggestion_id, callback);
 }
 
+void ContentSuggestionsService::FetchSuggestionFavicon(
+    const ContentSuggestion::ID& suggestion_id,
+    int minimum_size_in_pixel,
+    int desired_size_in_pixel,
+    const ImageFetchedCallback& callback) {
+  // TODO(jkrcal): Implement.
+}
+
 void ContentSuggestionsService::ClearHistory(
     base::Time begin,
     base::Time end,
     const base::Callback<bool(const GURL& url)>& filter) {
   for (const auto& provider : providers_) {
     provider->ClearHistory(begin, end, filter);
   }
   category_ranker_->ClearHistory(begin, end);
   // This potentially removed personalized data which we shouldn't display
   // anymore.
@@ skipping 372 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