Add request throttler to thumbnail fetching for articles on mobile NTP

components/ntp_snippets/request_throttler_unittest.cc

Index: components/ntp_snippets/request_throttler_unittest.cc
diff --git a/components/ntp_snippets/request_throttler_unittest.cc b/components/ntp_snippets/request_throttler_unittest.cc
index 97c2b0200bff81e275704ca3ae531e556b71ac68..9c485ecadd9b10639ee39ed6c233059caae4862a 100644
--- a/components/ntp_snippets/request_throttler_unittest.cc
+++ b/components/ntp_snippets/request_throttler_unittest.cc
@@ -62,7 +62,7 @@ TEST_F(RequestThrottlerTest, QuotaIsPerDay) {
   // Now fake the day pref so that the counter believes the count comes from
   // yesterday.
   int now_day = (base::Time::Now() - base::Time::UnixEpoch()).InDays();
-  test_prefs_.SetInteger(ntp_snippets::prefs::kSnippetFetcherQuotaDay,
+  test_prefs_.SetInteger(ntp_snippets::prefs::kSnippetFetcherRequestsDay,
                          now_day - 1);
 
   // The quota should get reset as the day has changed.