[NTP Snippets] Don't reschedule background fetching on every startup

components/ntp_snippets/pref_names.cc

Index: components/ntp_snippets/pref_names.cc
diff --git a/components/ntp_snippets/pref_names.cc b/components/ntp_snippets/pref_names.cc
index 53836bf508f04566684705c88c958222f1482d9b..aaaeedfa274ed3a17ee8d134f2b52cf8fe4de303 100644
--- a/components/ntp_snippets/pref_names.cc
+++ b/components/ntp_snippets/pref_names.cc
@@ -11,6 +11,12 @@ const char kEnableSnippets[] = "ntp_snippets.enable";
 
 const char kSnippetHosts[] = "ntp_snippets.hosts";
 
+const char kSnippetBackgroundFetchingIntervalWifi[] =
+    "ntp_snippets.fetching_interval_wifi";
+
+const char kSnippetBackgroundFetchingIntervalFallback[] =
+    "ntp_snippets.fetching_interval_fallback";
+
 const char kSnippetFetcherRequestCount[] =
     "ntp.request_throttler.suggestion_fetcher.count";
 const char kSnippetFetcherInteractiveRequestCount[] =