Ensure the 1993 NTP logs to UMA Most Visited tiles that use the fallback thumbnail instead of the p…

chrome/common/ntp_logging_events.h

Index: chrome/common/ntp_logging_events.h
diff --git a/chrome/common/ntp_logging_events.h b/chrome/common/ntp_logging_events.h
index 3a95a59932fd4cc6155fd6c9f44e6e4600ffa210..6ce3b126a4c054097f7b91693d5eda653ab025b0 100644
--- a/chrome/common/ntp_logging_events.h
+++ b/chrome/common/ntp_logging_events.h
@@ -16,6 +16,13 @@ enum NTPLoggingEventType {
   // There was an error in loading a thumbnail image.
   NTP_THUMBNAIL_ERROR = 2,
 
+  // The page attempted to load a thumbnail image and provided a fallback.
+  NTP_THUMBNAIL_WITH_FALLBACK_ATTEMPT = 3,
+
+  // The primary thumbnail image failed to load and caused a fallback to the
+  // secondary thumbnail.
+  NTP_THUMBNAIL_FALLBACK = 4,
+
   NTP_NUM_EVENT_TYPES
 };