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

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">
@@ skipping 24 matching lines @@
   // 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: 6,
   // Used a gray tile with the domain as the fallback for a failed thumbnail.
   NTP_GRAY_TILE_FALLBACK: 7,
   // The visuals of that tile's fallback are handled externally.
   NTP_EXTERNAL_TILE_FALLBACK: 8,
   // The user moused over an NTP tile or title.
-  NTP_MOUSEOVER: 9
+  NTP_MOUSEOVER: 9,
+  // A NTP Tile has finished loading (successfully or failing).
+  NTP_TILE_LOADED: 10,
 };
 
 /**
  * Type of the impression provider for a generic client-provided suggestion.
  * @type {string}
  * @const
  */
 var CLIENT_PROVIDER_NAME = 'client';
 
 /**
@@ skipping 244 matching lines @@
   if (navigator.sendBeacon) {
     navigator.sendBeacon(url);
   } else {
     // if sendBeacon is not enabled, we fallback for "a ping".
     var a = document.createElement('a');
     a.href = '#';
     a.ping = url;
     a.click();
   }
 }