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

chrome/browser/resources/local_ntp/most_visited_util.js

 // 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.
 
 
 /**
  * @fileoverview Utilities for rendering most visited thumbnails and titles.
  */
 
 <include src="instant_iframe_validation.js">
 
 /**
  * Enum for the different types of events that are logged from the NTP.
  * @enum {number}
  * @const
  */
 var NTP_LOGGING_EVENT_TYPE = {
   // The user moused over an NTP tile or title.
   NTP_MOUSEOVER: 0,
   // The page attempted to load a thumbnail image.
   NTP_THUMBNAIL_ATTEMPT: 1,
-  // There was an error in loading a thumbnail image.
-  NTP_THUMBNAIL_ERROR: 2
+  // 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
 };
 
 /**
  * Parses query parameters from Location.
  * @param {string} location The URL to generate the CSS url for.
  * @return {Object} Dictionary containing name value pairs for URL.
  */
 function parseQueryParams(location) {
   var params = Object.create(null);
   var query = location.search.substring(1);
@@ skipping 104 matching lines @@
       return;
   }
   if (/^javascript:/i.test(data.url) ||
       /^javascript:/i.test(data.thumbnailUrl) ||
       /^javascript:/i.test(data.thumbnailUrl2))
     return;
   if (data.direction)
     document.body.dir = data.direction;
   fill(params, data);
 }