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

chrome/browser/resources/ntp/drag_drop_controller.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.
 
 // The delegate interface:
 //   dragContainer -->
 //         element containing the draggable items
 //
 //   transitionsDuration -->
 //         length of time of transitions in ms
 //
 //   dragItem -->
 //         get / set property containing the item being dragged
 //
 //   getItem(e) -->
 //         get's the item that is under the mouse event |e|
 //
 //   canDropOn(coordinates) -->
 //         returns true if the coordinates (relative to the drag container)
 //         point to a valid place to drop an item
 //
 //   setDragPlaceholder(coordinates) -->
 //         tells the delegate that the dragged item is currently above
 //         the specified coordinates.
 //
-//   saveDrag() -->
+//   saveDrag(draggedItem) -->
 //         tells the delegate that the drag is done. move the item to the
-//         position last specified by setDragPlaceholder. (e.g., commit changes)
+//         position last specified by setDragPlaceholder (e.g., commit changes).
+//         draggedItem was the item being dragged.
 //
 
 // The distance, in px, that the mouse must move before initiating a drag.
 var DRAG_THRESHOLD = 35;
 
 function DragAndDropController(delegate) {
   this.delegate_ = delegate;
 
   // Install the 'mousedown' handler, the entry point to drag and drop.
   var el = this.delegate_.dragContainer;
@@ skipping 116 matching lines @@
   },
 
   handleDrop_: function() {
     this.disableHandlers_();
 
     var dragItem = this.delegate_.dragItem;
     if (!dragItem)
       return;
 
     this.delegate_.dragItem = this.startItem_ = null;
-    this.delegate_.saveDrag();
+    this.delegate_.saveDrag(dragItem);
     dragItem.classList.remove('dragging');
 
     setTimeout(function() {
       // Keep the flag around a little so other 'mouseup' and 'click'
       // listeners know the event is from a drag operation.
       this.isDragging_ = false;
       dragItem.style.zIndex = 0;
     }.bind(this), this.delegate_.transitionsDuration);
   },
 
@@ skipping 26 matching lines @@
 
     dragItem.style.left = x + 'px';
     dragItem.style.top = y + 'px';
 
     // Update the layouts and positions based on the new drag location.
     this.handleDragOver_();
 
     this.delegate_.scrollPage(this.mouseXY_);
   }
 };