Revert "Indexed DB: Remove nonstandard IDBFactory.webkitGetDatabaseNames()"

third_party/WebKit/LayoutTests/http/tests/security/resources/worker-for-indexeddb.js

 self.onmessage = function() {
     function test(method, args) {
         try {
             var request = self.indexedDB[method].call(self.indexedDB, args);
             return 'Successfully called self.indexedDB.' + method + '().<br>';
         } catch (exception) {
             return 'self.indexedDB.' + method + '() threw an exception: ' + exception.name + '<br>';
         }
     }
     self.postMessage({
         'result': [
             test('deleteDatabase', 'testDBName'),
             test('open', 'testDBName'),
+            test('webkitGetDatabaseNames')
         ]
     });
 };