[WebUI] Make drag'n'drop future proof.

chrome/browser/resources/ntp4/apps_page.js

 // Copyright (c) 2012 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('ntp', function() {
   'use strict';
 
   var localStrings = new LocalStrings;
 
   var APP_LAUNCH = {
@@ skipping 772 matching lines @@
       if (tile && !tile.querySelector('.app')) {
         e.preventDefault();
         this.setDropEffect(e.dataTransfer);
       } else {
         TilePage.prototype.doDragOver.call(this, e);
       }
     },
 
     /** @inheritDoc */
     shouldAcceptDrag: function(e) {
-      return !!ntp.getCurrentlyDraggingTile() ||
-          (e.dataTransfer && e.dataTransfer.types.contains('text/uri-list'));
+      if (ntp.getCurrentlyDraggingTile())
+        return true;
+      if (!e.dataTransfer || !e.dataTransfer.types)
+        return false;
+      return Array.prototype.indexOf.call(e.dataTransfer.types,
+                                          'text/uri-list') != -1;
     },
 
     /** @inheritDoc */
     addDragData: function(dataTransfer, index) {
       var sourceId = -1;
       var currentlyDraggingTile = ntp.getCurrentlyDraggingTile();
       if (currentlyDraggingTile) {
         var tileContents = currentlyDraggingTile.firstChild;
         if (tileContents.classList.contains('app')) {
           var originalPage = currentlyDraggingTile.tilePage;
@@ skipping 151 matching lines @@
       app.setupNotification_(notification);
   }
 
   return {
     APP_LAUNCH: APP_LAUNCH,
     appNotificationChanged: appNotificationChanged,
     AppsPage: AppsPage,
     launchAppAfterEnable: launchAppAfterEnable,
   };
 });