Most visited iframe now postMessage to signal the iframing page that the link has been displayed

chrome/common/ntp_logging_events.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_COMMON_NTP_LOGGING_EVENTS_H_
 #define CHROME_COMMON_NTP_LOGGING_EVENTS_H_
 
-// The different types of events that are logged from the NTP.
+// The different types of events that are logged from the NTP. This enum is used
+// to transfer information from the NTP javascript to the renderer and is not
+// used as a UMA enum histogram's logged value.
+// Note: Keep in sync with browser/resources/local_ntp/most_visited_utils.js
 enum NTPLoggingEventType {
-  // The user moused over an NTP tile or title.
-  NTP_MOUSEOVER = 0,
+  // The suggestion is coming from the server.
+  NTP_SERVER_SIDE_SUGGESTION = 0,
 
-  // The page attempted to load a thumbnail image.
-  NTP_THUMBNAIL_ATTEMPT = 1,
+  // The suggestion is coming from the client.
+  NTP_CLIENT_SIDE_SUGGESTION = 1,
+
+  // Indicates a tile was rendered, no matter if it's a thumbnail, a gray tile
+  // or an external tile.
+  NTP_TILE = 2,
+
+  // The tile uses a local thumbnail image.
+  NTP_THUMBNAIL_TILE = 3,
+
+  // Used when no thumbnail is specified and a gray tile with the domain is used
+  // as the main tile.
+  NTP_GRAY_TILE = 4,
+
+  // The visuals of that tile are handled externally by the page itself.
+  NTP_EXTERNAL_TILE = 5,
 
   // 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,
+  NTP_THUMBNAIL_ERROR = 6,
 
-  // The page attempted to load a thumbnail URL while a fallback thumbnail was
-  // provided.
-  NTP_FALLBACK_THUMBNAIL_REQUESTED = 3,
+  // Used a gray tile with the domain as the fallback for a failed thumbnail.
+  NTP_GRAY_TILE_FALLBACK = 7,
 
-  // The primary thumbnail image failed to load and caused us to use the
-  // secondary thumbnail as a fallback.
-  NTP_FALLBACK_THUMBNAIL_USED = 4,
+  // The visuals of that tile's fallback are handled externally.
+  NTP_EXTERNAL_TILE_FALLBACK = 8,
 
-  // The suggestion is coming from the server.
-  NTP_SERVER_SIDE_SUGGESTION = 5,
-
-  // The suggestion is coming from the client.
-  NTP_CLIENT_SIDE_SUGGESTION = 6,
-
-  // The visuals of that tile are handled externally by the page itself.
-  NTP_EXTERNAL_TILE = 7,
+  // The user moused over an NTP tile or title.
+  NTP_MOUSEOVER = 9,
 
   NTP_NUM_EVENT_TYPES
 };
 
 #endif  // CHROME_COMMON_NTP_LOGGING_EVENTS_H_