[NTP4] Track the position of each app that's launched.

chrome/browser/resources/ntp4/most_visited_page.js

 // Copyright (c) 2011 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.
 
 cr.define('ntp4', function() {
   'use strict';
 
   var TilePage = ntp4.TilePage;
 
   /**
@@ skipping 123 matching lines @@
       } else {
         // Records an app launch from the most visited page (Chrome will decide
         // whether the url is an app). TODO(estade): this only works for clicks;
         // other actions like "open in new tab" from the context menu won't be
         // recorded. Can this be fixed?
         chrome.send('recordAppLaunchByURL',
                     [encodeURIComponent(this.href),
                      ntp4.APP_LAUNCH.NTP_MOST_VISITED]);
         // Records the index of this tile.
         chrome.send('metricsHandler:recordInHistogram',
-                    ['NTP_MostVisited', this.index, 8]);
+                    ['NTP_MostVisited', this.index, THUMBNAIL_COUNT]);
       }
     },
 
     /**
      * Allow blacklisting most visited site using the keyboard.
      */
     handleKeyDown_: function(e) {
       if (!cr.isMac && e.keyCode == 46 || // Del
           cr.isMac && e.metaKey && e.keyCode == 8) { // Cmd + Backspace
         this.blacklist_();
@@ skipping 262 matching lines @@
     }
 
     return oldData;
   };
 
   return {
     MostVisitedPage: MostVisitedPage,
     refreshData: refreshData,
   };
 });