Adding UMA metric to record the type of suggestion displayed on the NTP's Most Visited section.

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 8bc8738b7fb08347b4999bbec76ef752757195ba..2b766c005782f9a9defe5bfce794773ab81ee5e4 100644
--- a/chrome/common/ntp_logging_events.h
+++ b/chrome/common/ntp_logging_events.h
@@ -25,6 +25,9 @@ enum NTPLoggingEventType {
   // secondary thumbnail as a fallback.
   NTP_FALLBACK_THUMBNAIL_USED = 4,
 
+  // The suggestion is coming from the server.
+  NTP_SERVER_SIDE_SUGGESTION = 5,
+
   NTP_NUM_EVENT_TYPES
 };