Track which apps the user has re-ordered on the NTP.

chrome/browser/resources/ntp/apps.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.
 
 var MAX_APPS_PER_ROW = [];
 MAX_APPS_PER_ROW[LayoutMode.SMALL] = 4;
 MAX_APPS_PER_ROW[LayoutMode.NORMAL] = 6;
 
 function getAppsCallback(data) {
   logEvent('received apps');
@@ skipping 506 matching lines @@
       var multiplier = Math.floor(Math.abs(delta) / 50) + 1;
 
       return sign * scalar * multiplier;
     },
 
     stopScroll_: function() {
       this.scrollListener_ = null;
       this.scrollMouseXY_ = null;
     },
 
-    saveDrag: function() {
+    saveDrag: function(draggedItem) {
       this.invalidate_();
       this.layout();
 
+      var draggedAppId = draggedItem.querySelector('a').getAttribute('app-id');
       var appIds = this.data.filter(function(id) {
         return id != 'web-store-entry';
       });
 
       // Wait until the transitions are complete before notifying the browser.
       // Otherwise, the apps will be re-rendered while still transitioning.
       setTimeout(function() {
-        chrome.send('reorderApps', appIds);
+        chrome.send('reorderApps', [draggedAppId, appIds]);
       }, this.transitionsDuration + 10);
     },
 
     layout: function(options) {
       options = options || {};
       if (!this.dirty_ && options.force != true)
         return;
 
       try {
         var container = this.dragContainer;
@@ skipping 155 matching lines @@
       a.href = localStrings.getString('web_store_url');
       a.style.backgroundImage = url('chrome://theme/IDR_PRODUCT_LOGO_16');
       a.className = 'item';
       return a;
     }
   };
 })();
 
 // Enable drag and drop reordering of the app launcher.
 var appDragAndDrop = new DragAndDropController(apps);