NTP4: Dragging app over trash should be more apparent.

chrome/browser/resources/ntp4/trash.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.
 
 /**
  * @fileoverview Trash
  * This is the class for the trash can that appears when dragging an app.
  */
 
 cr.define('ntp4', function() {
@@ skipping 25 matching lines @@
       return tile.firstChild.canBeRemoved();
     },
 
     /**
      * Drag over handler.
      * @param {Event} e The drag event.
      */
     doDragOver: function(e) {
       ntp4.getCurrentlyDraggingTile().dragClone.classList.add(
           'hovering-on-trash');
+      this.classList.add('could-drop');
       ntp4.setCurrentDropEffect(e.dataTransfer, 'move');
       e.preventDefault();
     },
 
     /**
      * Drag enter handler.
      * @param {Event} e The drag event.
      */
     doDragEnter: function(e) {
       this.doDragOver(e);
     },
 
     /**
      * Drop handler.
      * @param {Event} e The drag event.
      */
     doDrop: function(e) {
       e.preventDefault();
 
       var tile = ntp4.getCurrentlyDraggingTile();
       tile.firstChild.removeFromChrome();
       tile.landedOnTrash = true;
+      this.classList.remove('could-drop');
     },
 
     /**
      * Drag leave handler.
      * @param {Event} e The drag event.
      */
     doDragLeave: function(e) {
       ntp4.getCurrentlyDraggingTile().dragClone.classList.remove(
           'hovering-on-trash');
+      this.classList.remove('could-drop');
     },
   };
 
   return {
     Trash: Trash,
   };
 });