Adds a new UMA histogram to measure the NTP load time since navigation

chrome/browser/resources/local_ntp/most_visited_thumbnail.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 Rendering for iframed most visited thumbnails.
  */
 
 window.addEventListener('DOMContentLoaded', function() {
@@ skipping 36 matching lines @@
       image.onload = function() {
         var link = createMostVisitedLink(
             params, data.url, data.title, undefined, data.direction,
             data.provider);
         // Use blocker to prevent context menu from showing image-related items.
         var blocker = document.createElement('span');
         blocker.className = 'blocker';
         link.appendChild(blocker);
         link.appendChild(image);
         displayLink(link);
+        logEvent(NTP_LOGGING_EVENT_TYPE.NTP_TILE_LOADED);
       };
       image.onerror = function() {
         // If no external thumbnail fallback (etfb), and have domain.
         if (!params.etfb && data.domain) {
           showDomainElement();
           logEvent(NTP_LOGGING_EVENT_TYPE.NTP_GRAY_TILE_FALLBACK);
         } else {
           showEmptyTile();
           logEvent(NTP_LOGGING_EVENT_TYPE.NTP_EXTERNAL_TILE_FALLBACK);
         }
         logEvent(NTP_LOGGING_EVENT_TYPE.NTP_THUMBNAIL_ERROR);
+        logEvent(NTP_LOGGING_EVENT_TYPE.NTP_TILE_LOADED);
       };
       image.src = src;
     }
 
     if (data.dummy) {
       showEmptyTile();
       logEvent(NTP_LOGGING_EVENT_TYPE.NTP_EXTERNAL_TILE);
     } else if (data.largeIconUrl) {
       createThumbnail(data.largeIconUrl, 'large-icon');
       // TODO(huangs): Log event for large icons.
     } else if (data.thumbnailUrl) {
       createThumbnail(data.thumbnailUrl, 'thumbnail');
       logEvent(NTP_LOGGING_EVENT_TYPE.NTP_THUMBNAIL_TILE);
     } else if (data.domain) {
       showDomainElement();
       logEvent(NTP_LOGGING_EVENT_TYPE.NTP_GRAY_TILE);
     } else {
       showEmptyTile();
       logEvent(NTP_LOGGING_EVENT_TYPE.NTP_EXTERNAL_TILE);
     }
     logEvent(NTP_LOGGING_EVENT_TYPE.NTP_TILE);
 
     // Log an impression if we know the position of the tile.
     if (isFinite(params.pos) && data.provider) {
       logMostVisitedImpression(parseInt(params.pos, 10), data.provider);
     }
   });
 });