ntp4: polish app trashing

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 11 matching lines @@
     initialize: function(element) {
       this.dragWrapper_ = new DragWrapper(this, this);
     },
 
     /**
      * Determines whether we are interested in the drag data for |e|.
      * @param {Event} e The event from drag enter.
      * @return {bool}
      */
     shouldAcceptDrag: function(e) {
-      return !!ntp4.getCurrentlyDraggingTile().querySelector('.app');
+      var tile = ntp4.getCurrentlyDraggingTile();
+      if (!tile)
+        return false;
+
+      var app = tile.querySelector('.app');
+      if (!app)
+        return false;
+
+      return app.appData.can_uninstall;
     },
 
     /**
      * Drag over handler.
      * @param {Event} e The drag event.
      */
     doDragOver: function(e) {
+      ntp4.getCurrentlyDraggingTile().dragClone.classList.add(
+          'hovering-on-trash');
       e.preventDefault();
       e.dataTransfer.dropEffect = 'move';
     },
 
     /**
      * Drag enter handler.
      * @param {Event} e The drag event.
      */
     doDragEnter: function(e) {
       this.doDragOver(e);
@@ skipping 16 matching lines @@
       var page = tile.tilePage;
       tile.parentNode.removeChild(tile);
       page.cleanupDrag();
     },
 
     /**
      * Drag leave handler.
      * @param {Event} e The drag event.
      */
     doDragLeave: function(e) {
+      ntp4.getCurrentlyDraggingTile().dragClone.classList.remove(
+          'hovering-on-trash');
     },
   };
 
   return {
     Trash: Trash,
   };
 });