[SuggestionsService] Split SuggestionsService interface from impl

ios/chrome/browser/suggestions/suggestions_service_factory.mm

Index: ios/chrome/browser/suggestions/suggestions_service_factory.mm
diff --git a/ios/chrome/browser/suggestions/suggestions_service_factory.mm b/ios/chrome/browser/suggestions/suggestions_service_factory.mm
index 2e9f464130b7b1182689fe328f4e5a8d14cbdcee..3b361f8edd3b6fcce137c3499774e8b4489a43fa 100644
--- a/ios/chrome/browser/suggestions/suggestions_service_factory.mm
+++ b/ios/chrome/browser/suggestions/suggestions_service_factory.mm
@@ -90,7 +90,7 @@ SuggestionsServiceFactory::BuildServiceInstanceFor(
   std::unique_ptr<ImageManager> thumbnail_manager(new ImageManager(
       std::move(image_fetcher), std::move(db), database_dir,
       web::WebThread::GetTaskRunnerForThread(web::WebThread::DB)));
-  return base::MakeUnique<SuggestionsService>(
+  return base::MakeUnique<SuggestionsServiceImpl>(
       signin_manager, token_service, sync_service,
       browser_state->GetRequestContext(), std::move(suggestions_store),
       std::move(thumbnail_manager), std::move(blacklist_store));
@@ -98,7 +98,7 @@ SuggestionsServiceFactory::BuildServiceInstanceFor(
 
 void SuggestionsServiceFactory::RegisterBrowserStatePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
-  SuggestionsService::RegisterProfilePrefs(registry);
+  SuggestionsServiceImpl::RegisterProfilePrefs(registry);
 }
 
 }  // namespace suggestions