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..8bc8738b7fb08347b4999bbec76ef752757195ba 100644
--- a/chrome/common/ntp_logging_events.h
+++ b/chrome/common/ntp_logging_events.h
@@ -13,9 +13,18 @@ enum NTPLoggingEventType {
   // The page attempted to load a thumbnail image.
   NTP_THUMBNAIL_ATTEMPT = 1,
 
-  // There was an error in loading a thumbnail image.
+  // There was an error in loading both the thumbnail image and the fallback
+  // (if it was provided), resulting in a grey tile.
   NTP_THUMBNAIL_ERROR = 2,
 
+  // The page attempted to load a thumbnail URL while a fallback thumbnail was
+  // provided.
+  NTP_FALLBACK_THUMBNAIL_REQUESTED = 3,
+
+  // The primary thumbnail image failed to load and caused us to use the
+  // secondary thumbnail as a fallback.
+  NTP_FALLBACK_THUMBNAIL_USED = 4,
+
   NTP_NUM_EVENT_TYPES
 };