Add request throttler to thumbnail fetching for articles on mobile NTP

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 67e1dc64b30b246b755e1ff51c69b073b0eddaa2..a7787c806c1a7245116c5cdff732d2e2de6c808c 100644
--- a/components/ntp_snippets/pref_names.cc
+++ b/components/ntp_snippets/pref_names.cc
@@ -15,6 +15,15 @@ const char kSnippetFetcherQuotaDay[] =
     "ntp.request_throttler.suggestion_fetcher.day";
 const char kSnippetFetcherQuotaCount[] =
     "ntp.request_throttler.suggestion_fetcher.count";
+const char kSnippetFetcherInteractiveQuotaCount[] =
+    "ntp.request_throttler.suggestion_fetcher.interactive_count";
+
+const char kSnippetThumbnailsQuotaDay[] =
+    "ntp.request_throttler.suggestion_thumbnails.day";
+const char kSnippetThumbnailsQuotaCount[] =
+    "ntp.request_throttler.suggestion_thumbnails.count";
+const char kSnippetThumbnailsInteractiveQuotaCount[] =
+    "ntp.request_throttler.suggestion_thumbnails.interactive_count";
 
 }  // namespace prefs
 }  // namespace ntp_snippets