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

chrome/browser/resources/ntp4/apps_page.js

Index: chrome/browser/resources/ntp4/apps_page.js
diff --git a/chrome/browser/resources/ntp4/apps_page.js b/chrome/browser/resources/ntp4/apps_page.js
index fbe0d4dddb5dd44dbf7f8b7bab216e09f165a9e8..d3a701ee6c7ea5364238c6fcb50f9d194a7c0957 100644
--- a/chrome/browser/resources/ntp4/apps_page.js
+++ b/chrome/browser/resources/ntp4/apps_page.js
@@ -790,8 +790,12 @@ cr.define('ntp', function() {
 
     /** @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 */