Add gated cover byte fetcher

backend/main.go

@@ -343,8 +343,8 @@ func main() {
 
 // newLatestPoller wires the configured cooldowns and fetchers into the poller.
 func newLatestPoller(s *store.Store, cfg LatestPoll, fetch, browser latest.Fetcher) *latest.Poller {
-	var covers latest.CoverFetcher
-	if f, ok := browser.(latest.CoverFetcher); ok {
+	var covers latest.BrowserCoverFetcher
+	if f, ok := browser.(latest.BrowserCoverFetcher); ok {
 		covers = f
 	}
 	return &latest.Poller{
@@ -352,6 +352,7 @@ func newLatestPoller(s *store.Store, cfg LatestPoll, fetch, browser latest.Fetch
 		Fetch:           fetch,
 		BrowserFetch:    browser,
 		CoverFetch:      covers,
+		CoverBytesFetch: latest.NewCoverFetcher(),
 		Now:             time.Now,
 		Cooldown:        cfg.Cooldown,
 		BrowserCooldown: cfg.BrowserCooldown,