NTP Snippets: Added error codes for out of quota events

components/ntp_snippets/ntp_snippets_fetcher.cc

Index: components/ntp_snippets/ntp_snippets_fetcher.cc
diff --git a/components/ntp_snippets/ntp_snippets_fetcher.cc b/components/ntp_snippets/ntp_snippets_fetcher.cc
index c0018e7d816ad650ff06f25bdf664b5b64034e2e..c040af7b25f331ca4eccae7d55bc6217ba97c32b 100644
--- a/components/ntp_snippets/ntp_snippets_fetcher.cc
+++ b/components/ntp_snippets/ntp_snippets_fetcher.cc
@@ -86,6 +86,10 @@ std::string FetchResultToString(NTPSnippetsFetcher::FetchResult result) {
       return "Invalid / empty list.";
     case NTPSnippetsFetcher::FetchResult::OAUTH_TOKEN_ERROR:
       return "Error in obtaining an OAuth2 access token.";
+    case NTPSnippetsFetcher::FetchResult::INTERACTIVE_QUOTA_ERROR:
+      return "Out of interactive quota.";
+    case NTPSnippetsFetcher::FetchResult::NON_INTERACTIVE_QUOTA_ERROR:
+      return "Out of non-interactive quota.";
     case NTPSnippetsFetcher::FetchResult::RESULT_MAX:
       break;
   }
@@ -218,8 +222,15 @@ void NTPSnippetsFetcher::FetchSnippetsFromHosts(
     const std::string& language_code,
     int count,
     bool interactive_request) {
-  if (!request_throttler_.DemandQuotaForRequest(interactive_request))
+  if (!request_throttler_.DemandQuotaForRequest(interactive_request)) {
+    FetchFinished(
+        OptionalSnippets(),
+        interactive_request ?
+          FetchResult::INTERACTIVE_QUOTA_ERROR :
+          FetchResult::NON_INTERACTIVE_QUOTA_ERROR,
+          /*extra_message=*/std::string());
     return;
+  }
 
   hosts_ = hosts;
   fetch_start_time_ = tick_clock_->NowTicks();